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Acanthochlamydaceae

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Acanthochlamydaceae Kao P.-C., Fl. Sichuan. 9: 483 (1989).

Dwarf caespitose perennial herb; rhizome short; roots dense, thin and long, fibriform; leaves acerose, dorsiventral, ventrally subsemiorbicular and 2-canaliculate, dorsally flattened and 1-canaliculate, sheathed at the base. Inflorescence a compound capitulum on a scape arising from the rhizome, at the base usually surrounded by 3 leaflike aristate bracts, the peduncle bearing 5-8 few-flowered capitula, the flowers subtended by aristate bractlets. Flowers hermaphroditic, actino-morphic, epigynous, shortly pedicellate; perianth corollinic, pink, tubular; perianth lobes 3 + 3, the inner lobes slightly smaller than the outer; stamens 3 + 3, borne upon the corolla lobes; filaments short; anthers oblong, bisporangiate, dorsifixed, introrse, dehiscing by longitudinal slits; ovary inferior, syncarpous, in lower part trilocular with axile placentation, in upper part unilocular with parietal placentation; ovules numerous, anatropous, bitegmic; style elongate, with trilobate stigma; fruit capsular, trigonous, shortly rostrate; seeds oblong, brown; endosperm starch-containing; embryo large, central.

Only one sp., Acanthochlamys bracteata P.C. Kao, subalpine xerophytic valley zone of W Sichuan and SE Tibet, SW China.

Vegetative Structures. The vascular cylinder of the root is a tetrarch, rarely triarch, actinostele lacking pith; this low number of xylem rays is unusual in monocotyledons. The root epidermis is formed by elongate cells which bear the root hairs. The cortex is composed of many cell layers and is divided into exodermis, cortex and endodermis. The cells of the pericycle are 1-rowed and densely arranged; the lateral roots originate from them.

The aerial parts are covered by elongate, thick-walled epidermal cells and bear sunken stomata which are paracytic. Massive sclerenchyma underlies the epidermis. In the leaves, the mesophyll lacks differentiation into palisade and spongy tissue. The midrib of the leaf is composed of 2 vascular bundles, which are arranged "back to back" with their xylem portions. The scape has on one side a longitudinal groove and hence in transversal section is indistinctly heart-shaped. Its anatomical structure is very peculiar insofar that it has a stele with a central tetrach vascular cylinder similar to that of the roots, which in the upper portion of the scape disintegrates into 5 or 6 collateral bundles. Outside the stelar tissue the inner part of the cortex is sclerified and underneath the longitudinal groove of the scape the cortex is transversed by 2 obliquely oriented vascular bundles (a leaf trace which supplies an involucral bract), which resemble those forming the leaf midrib but are fused with their xylem portions. The structure of the scape is similar to that of a leaf ensheathing a rhizome. Vessel elements with simple perforations and helical thickenings are present in the root, scape and leaf. Raphides and tannin cells are lacking completely (Kao 1989).

Embryology. The anther is bisporangiate (Fig. 20), and the anther wall is of the monocotyledon-ous type. The tapetum is glandular. Microsporo-genesis is of the Successive type; the pollen tetrads are isobilateral. The mature pollen grains are bi-or trinucleate. The ovule is anatropous, bitegmic and tenuinucellate. The development of the embryo sac is of the Polygonum type or Allium type (Li et al. 1992). Fertilisation is porogamous and premitotic and endosperm development is Nuclear (Li and Gao 1993).

Pollen Morphology. The pollen of Acanthochlamys is sulcate, spheroidal and (under SEM) finely verrucate to reticulate (Gao 1987).

1. Kao et al. (1993) reported the chromosome number 2n = 38.
2. The anthesis of Acanthochlamys is very short. Pollination seems to be mediated by small bees.
3. The seeds (Fig. 22) are brown, shining, ellipsoid, 0.75 X 0.5 mm. The epidermis of the outer integument is collapsed so that the seeds have a grooved, microreticulate surface. The other layer(s) belonging to the outer integument -certainly not more than 2 - is/are collapsed. The inner integument is represented by one well-developed and another collapsed layers that contain a red-brown content, presumably condensed tannins. Mechanical strength is provided mainly by the thickened peridinal walls of the cell layer immediately beneath the seed coat. This layer con-

Fig. 20A3. Acanthochlamydaceae. Acantkochlamys bracteata. A Transversal section of flower bud, showing stamens with 1-sporangiate thecae. B Part of stamen in transversal section; pollen mother cells after first meiotic division

tains aleuron and is free of starch. The rest of the endosperm contains starch in the form of composed starch grains. The embryo lies in the middle of the endosperm and reaches 3/4 of the length

1. 21A-C Acanthochlamydaceae. Acanthochlamys bracteata. A Seed, transversal section. B Seed, longitudinal section. C As A, enlarged, a Endosperm; b embryo; c seed coat; d aleurone layer; e cell filled with aleurone;/cell full of starch grains
2. 21A-C Acanthochlamydaceae. Acanthochlamys bracteata. A Seed, transversal section. B Seed, longitudinal section. C As A, enlarged, a Endosperm; b embryo; c seed coat; d aleurone layer; e cell filled with aleurone;/cell full of starch grains

of the endosperm (Kao 1989; H. Huber, pers. comm.).

1. According to a preliminary study (B.C. Gao, unpubl.) alkaloids are lacking, but steroid saponins may be present. Fluorescent ferulate is absent from the cell walls (Rudall 1994).
2. Originally described by Kao (1980) as a member of the Amaryllidaceae, Acanthochlamys was elevated to subfamily rank in Amaryllidaceae by Chen (1981). After studying the anatomy, taxonomy, palynology, embryology, karyology, phytochemistry and ecology of Acanthochlamys for nearly 10 years, the profound differences separating the genus from the Amaryllidaceae led Kao (1989) to elevate it to the rank of family. A close relationship to the Velloziaceae had been proposed by Gao (1987), but subsequently, Kao (1989) compared Acanthochlamys with Tofieldia and suggested for Acanthochlamys an intermediate position between Tofieldia and Amaryllidaceae. Later, and mainly based on the agreement in chromosome base number, a close relationship of Acanthochlamys to Convallariaceae (Aspidistra

Fig. 22A-L. Acanthochlamydaceae. Acanthochlamys brac-teata. A Habit. B Flower. C Flower, perianth opened. D Transsection of ovary. E Stigma. F Anther. G Flower bract. H, I Leaf sheath. J Fruit. K Seed. L Rhfeome

chlamys in the collapsed testa and 2-layered tegmen, the Velloziaceae also in the bisporangiate anthers, and additionally the Haemodoraceae in the thickened outer periclinal wall of the aleuron layer. Also the Xyridaceae are similar in several respects, although they are truly "enantioblastic" and have hypogynous flowers.

Among all families compared here with Acanthochlamys, the absence of cell wall-bound ferulate is shared only with the Velloziaceae. Thus the morphological data point in the same direction as the molecular analysis, although the relationship between Acanthochlamys and the Velloziaceae may not be very close.

Distribution and Habitats. Acanthochlamys bracteata is restricted to the Hengduan Mountains at the SE margin of the Kang-Zang Plateau of SW China (Xiangcheng, Daocheng, Daofu of W Sichuan to Zhag'yab of Tibet), where it occurs in the subalpine aciculignose shrub-meadow region at an altitude of 2700-3500m.

Only one genus:

Acanthochlamys P.C. Kao Figs. 20-22

Acanthochlamys P.C. Kao, Acta Phytotax. Chengdu Inst. Biol. Acad. Sin. 1:1 (1980).

Only one sp., description and distribution as for family.

and Tupistra) was considered (Kao et al. 1993); however, this suggestion is not supported by morphological evidence and is no longer upheld. In the rbcL analysis by Chase et al. (1995) Acanthochlamys appeared in a strongly supported branch together with the Velloziaceae.

Indeed, a possible relationship should be considered with all those families that share with Acanthochlamys the possession of epigyny and starch accumulation in the endosperm, viz. Bromeliaceae, Haemodoraceae and Velloziaceae. It is significant that these three families agree with Acanthochlamys in having starch grains composed of relatively few elements in the endosperm. Among these families, the Bromeliaceae differ-too much from Acanthochlamys in their perianth differentiated into calyx and corolla and their epidermal cells containing large silica bodies. The remaining two families agree with Acantho-

Selected Bibliography

Chase, M.W. et al. 1995. See general references.

Chen, S.-C. 1981. Acanthochlamydoideae - a new subfamily of Amaryllidaceae. Acta Phytotaxon. Sin. 19: 323-329. (In Chinese with Engl, summ.)

Gao, B.-C. 1987. The sociological characteristics and pollen morphology of Acanthochlamys. Acta Bot. Yunnan. 9: 401405. (In Chinese with Engl, summ.)

Gao, B.-C., Li, P. 1993. Studies on the morphology and embryology of Acanthochlamys bracteata I. Morphological and anatomic studies on vegetative organs. J. Sichuan Univ. (Science ed.) 30: 534-537. (In Chinese with Engl, summ.)

Kao, P.-C. 1980. A new genus of Amaryllidaceae from China. Acta phytotax. Chengdu Inst. Biol. Acad. Sin. 1: 1-3, pi. 111. (In Chinese and Latin)

Kao, P.-C. 1989. Acanthochlamydaceae - a new monocotyle-donous family. Fl. Sichuan (Kao, P.C., Tan, Z.-M., eds.) 9: 483-507, pi. I-IX. (In Chinese and Engl.)

Kao, P.-C., Tang, Y., Guo, W.-H. 1993. A cytological study of Acanthochlamys bracteata P.C. Kao (Acanthochlamydaceae). Acta Phytotaxon. Sin. 31: 42-44. (In Chinese with Engl, summ.)

Li, P., Gao, B.-C. 1993. Studies on morphology of Acanthochlamys bracteata. III. The investigation on double fertilization, embryogenesis and endosperm development of Acanthochlamys bracteata. ]. Sichuan Univ. (Science ed.) 30: 260-263, Figs. 1-18. (In Chinese with Engl, summ.) Li, P., Gao, B.-C., Chen, F., Luo, H.X. 1992. Studies on morphology and embryology of Acanthochlamys bracteata. II. The anther and ovule development. Bull. Bot. Res. 12:389395. (In Chinese with Engl, summary) Rudall, P. 1994. See general references.

Agapanthaceae

K. Kubitzki

Agapanthaceae Voigt, Gesch. Pflanzenwelt 2: 440 (1850), Agapantheae.

Perennials from a tuberous, erect rhizome; roots fleshy, provided with a multiple velamen. Leaves rosulate, distichously arranged, linear, slightly contracted between the sheath and linear, flat blade, slightly fleshy or leathery, margins smooth, hyaline or ridged. Inflorescence a pseudo-umbel subtended by 2 deciduous involucral spathal bracts; scape stout, terete or slightly compressed; pedicels erect, spreading or cernuous, subtended by persistent, threadlike bracts. Flowers trimer-ous, hermaphrodite, hypogynous, zygomorphic; perigone tubular or infundibuliform, tepals 6, subequal, basally ± fused, blue or white, the outer face with a median ridge, the inner grooved along the same line; outer segments narrower than inner and often slightly hooded, thickened, and uncinate or bearded at the apex, somewhat fleshy; stamens 6, inserted on the tube; filaments declinate, of unequal length; anthers dorsifixed, introrse with longitudinal dehiscence; ovary superior, sessile, ovoid or oblong, trilocular; inner septal nectaries present; ovules numerous, bitegmic; style slender, hollow, declinate, stigma small, of the dry type. Fruit a loculicidal capsule with many flat, black, winged seeds. 2n = 30, rarely 32.

Only one genus of 9 spp. endemic to South Africa from the Cape to the Limpopo River.

1. The roots have a multiple velamen (Goebel 1933). Laticifers have been reported by Hegnauer (1963). Vessels are present only in the roots, mostly with scalariform perforations. Raphides are present.
2. Various Agapanthus species are reported as having 2n = 30 (very rarely 32) (Satd 1942; Leighton 1965).

Pollen Morphology. Pollen of Agapanthus is sulcate-reticulate (Schulze 1980).

Embryology. Endothecial thickenings in the stamens consist of incomplete loops. Tapetum cells

Fig. 23A-E. Agapanthaceae. Agapanthus umbellatus. A Habit. B Scape with pseudoumbel. C Flower. D Young fruit. E Capsule. (Krause 1930)

are predominantly binucleate. Microsporogenesis is successive (Stenar 1933; Rudall et al. 1997).

1. The seeds of Agapanthus are angulate, elongated, half-campylotropous, and winged opposite the micropyle; the phytomelan crust is thin. The endosperm stores aleuron, oil and reserve cellulose. The embryo is well developed and reaches 4/5 of the length of the endosperm (Huber 1969).
2. Various steroid saponins have been isolated from the genus (Hegnauer 1963, 1986).
3. The older concepts of a family Agapanthaceae as proposed by Voigt (1850) and Lotsy (1911) were based on superficial similarities and need not be discussed here. In more recent classifications, Agapanthus and Tulbaghia form a subfamily, Agapanthoideae, of Alliaceae (Huber 1969; Dahlgren et al. 1985). However, these two genera differ considerably and Dahlgren et al. (1985) have argued that they may form a heterogeneous assemblage. This is certainly true because, for instance, raphides are lacking in Tulbaghia (as in most other Alliaceae) and are present in Agapanthus; Tulbaghia has a corona, which is lacking in Agapanthus; Tulbaghia has a solid style, Agapanthus a hollow style (Fay and Chase 1996); the chromosome base number of Tulbaghia is x = 6, that of Agapanthus 15 and 16; the embryo sac of Tulbaghia develops according to the Sciila type, that of Agapanthus follows the Polygonum type; a parietal cell is lacking in Tulbaghia, but present in Agapanthus; Tulbaghia has alliaceous chemistry, Agapanthus accumulates steroid saponins. In short, Tulbaghia definitely is alliaceous, Agapanthus not.

The molecular (rbcL) studies by Chase et al. (1995) and Fay and Chase (1996) have provided support for the inclusion of Tulbaghia in Alliaceae and have suggested Agapanthus as a sister to Amaryllidaceae. Fay and Chase (1996) proposed including Agapanthus as a monotypic subfamily in Amaryllidaceae in order to avoid the proliferation of families. However, characters such as the superior ovary of Agapanthus in contrast to the inferior ovary of all Amaryllidaceae and the steroidal saponin chemistry of Agapanthus in opposition to the specialized amaryllidaceous alkaloids of the Amaryllidaceae do not recommend this inclusion. The elevation of Agapanthus to family rank seems best to reflect present knowledge and is in accord with the narrow family concept practiced in this book. It is clear that this new family is closely related to Amaryllidaceae and Alliaceae.

Distribution and Habitats. The genus Agapanthus is distributed from the Cape Peninsula to the mountain ranges south of the Limpopo River.

Its range of altitude extends from sea level to 2300 m. Species growing in the southern part of the range of the genus in the Cape Province, where rain falls in the winter or throughout the year, are evergreen. Further to the north in the summer rain region of Natal and Transvaal, species lose all their leaves in the autumn and after lying dormant for 1-2 months produce an entirely new set of leaves in the spring (Leighton 1965).

Only one genus:

Agapanthus L'Hir. Fig. 23

Agapanthus L'H£r„ Sert. Angl.: 17 (1788); Leighton, J.S. Afr. Bot. Suppl. Vol. 4: 1-50 (1965), rev.

Description as of family. Nine spp., South Africa.

Selected Bibliography

Chase, M.W. et al. 1995. See general references. Dahlgren et al. 1985. See general references. Fay, M.F, Chase, M.W. 1996. Resurrection of Themidaceae for the Brodiaea alliance, and recircumscription of Alliaceae, AmaryUidaceae and Agapanthoideae. Taxon. 45:441-451. Goebel, K. 1933. Organographie der Pflanzen. 3. Teil: Samenpflanzen. Jena: G. Fischer. Hegnauer, R. 1963, 1986. See general references. Huber, H. 1969. See general references. Johri, M.M. 1966. The style, stigma, and pollen tube. III. Some taxa of the AmaryUidaceae. Phytomorphology 16: 142-157. Krause, K. 1930. See general references. Leighton, F.M. 1965. The genus Agapanthus L'Héritier. J.

South Afr. Bot, Suppl. 4: 50. Lotsy, P.J. 1911. Vorträge über botanische Stammesgeschichte, Vol. 3,1. Jena: G. Fischer. Rudall, P.J, Furness, C.A, Chase, M.W, Fay, M.F. 1997. Microsporogenesis and pollen sulcus type in Asparagales (Lilianae). Can. J. Bot. 75: 408-430. Satô, D. 1942. Karyotype alteration and phylogenyin Liliaceae and allied families. Jpn. J. Bot. 12: 57-161. Schulze, W. 1980. Beiträge zur Taxonomie der Liliifloren V. Alliaceae. Wiss. Z. Friedrich Schiller-Univ. Jena, Math. Naturwiss. Reihe 29: 595-606. Stenar, H. 1933. Zur Embryologie der Agapanthus-Gruppe.

Bot. Not. 1933: 520-530. Tamura, M.N. 1985. See general references. Voigt, F.S. 1850. Geschichte des Pflanzenreiches 2 Vols. Jena: F. Mauke.

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