NOVON 10(1): 1-3. 2000.

Status and Relationships of the Chinese Endemic Platycraspedum (Brassicaceae)

Ihsan Al-Shehbaz

Missouri Botanical Garden, P.O. Box 299, St. Louis, Missouri 63166-0299, U.S.A.

Cheo Taiyien, Lu lianli

Herbarium, Jiangsu Institute of Botany, Nanjing, Jiangsu 210014, People’s Republic of China

Yang Guang

Piroche Plants, Inc., 20542 McNeil Road, Pitt Meadows, B.C., Canada V3Y 1Z1

Abstract. The generic limits and relationships of Platycraspedum are discussed, and the new species P. wuchengyii is described. It is most closely related to Taphrospermum, from which it differs by having toothed filaments of median stamens, 2-lobed stigmas, palmately veined leaves, unequal sepals, and minutely reticulate seeds.

As delimited here, Platycraspedum O. E. Schulz consists of two Chinese species endemic to eastern Xizang (Tibet) and neighboring Sichuan. Schulz (1922) compared the generic type, P. tibeticum, with Dilophia Thomson and later (Schulz, 1936) placed both genera in the tribe Lepidieae. However, Platycraspedum does not have angustiseptate fruits, a feature Schulz (1936) used primarily to define the limits of Lepidieae. In our opinion, Platycraspedum, along with Dilophia, Taphrospermum C. A. Meyer, Lignariella Baehni, and several other genera, should be closely associated with Cardamine L., all of which share flattened replums, a feature not known elsewhere in the Brassicaceae. The present paper does not aim to present the tribal alignments of these genera; nonetheless Schulz’s (1936) placement of Platycraspedum in the Lepidieae is unwarranted.

Platycraspedum is most closely related to Taphrospermum, a genus of seven species (Al-Shehbaz, unpublished) distributed primarily in China. Both genera have fleshy fusiform roots, a whorl of scalelike leaves at the root base, petiolate cauline leaves, bracteate inflorescences, white petals, basally dilated median filaments, and flattened replums. Platycraspedum is readily separated from Taphrospermum by its palmately veined cauline leaves and bracts, minutely reticulate seeds, strongly flattened and toothed median staminal filaments, unequal sepals with the lateral pair saccate, poorly developed lateral nectaries with the median ones lacking, and 2-lobed stigmas. By contrast, Taphrospermum has pinnately veined cauline leaves and bracts, foveolate or rarely papillate seeds, terete and toothless filaments, equal and nonsaccate sepals, well-developed annular lateral nectaries confluent with median ones, and entire stigmas.

Platycraspedum can easily be confused with some species of Eutrema R. Brown sect. Wasabia (Matsumura) O. E. Schulz, but it can be separated by its strongly flattened and 1-toothed median filaments, flattened replums, non-mucronate leaf teeth, subsessile fruits, unequal sepals with the inner pair saccate, 2-lobed stigmas, and lack of septa. Eutrema has slender and toothless median filaments, terete replums, mucronate teeth or leaf-vein endings, stipitate fruits, equal sepals with the inner pair nonsaccate, entire stigma, and complete septum.

Although the two species of Platycraspedum are quite different in fruit morphology (see key), we believe that their shared characters (fleshy taproots, fully bracteate inflorescences, petiolate, palmately veined cauline leaves, non-mucronate leaf marginal teeth, white flowers, unequal sepals with inner pair saccate, flattened and toothed median filaments, 2-lobed stigmas, flattened replums, absence of septa, and accumbent flattened seeds) provide ample evidence to treat them as congeneric.

Platycraspedum O. E. Schulz, Repert. Sp. Nov. Regni Veg. Beih. 12: 386. 1922. TYPE: Platycraspedum tibeticum O. E. Schulz.

Herbs biennial or perennial. Trichomes simple. Roots fusiform, fleshy. Stems erect, short, and simple at base, with several, long, decumbent to ascending branches. Basal leaves absent. Cauline leaves petiolate, repand-dentate to palmately lobed, the lobes not mucronate, base cordate. Racemes several-flowered, terminal, corymbose, bracteate throughout, elongated considerably in fruit. Sepals oblong (outer pair) or broadly ovate (inner), deciduous, glabrous, unequal, base of inner pair saccate, margins membranous. Petals white, narrowly obovate to subelliptic. Stamens 6, tetradynamous; filaments white; median pair strongly flattened, laterally 1-toothed; anthers oblong. Nectar glands 2, annular, lateral; median nectaries absent. Ovules 3 to 9 per ovary. Fruit dehiscent siliques, linear to oblong, terete or 4-angled, short stipitate; valves obscurely veined or with a prominent, narrowly winged midvein, keeled or not keeled; gynophore short and rarely to 1 mm long; replum flattened, winged or wingless; septum absent; style to 1.5 mm long; stigma 2-lobed. Seeds uniseriate, wingless, oblong to ovate, flattened; seed coat minutely reticulate, not mucilaginous when wetted; cotyledons accumbent.

Key to the Species of Platycraspedum

1a. Fruit 4-angled, narrowly 4-winged, not torulose, 2.5--3 mm wide; petals 4--6 ´ 2--3 mm;

seeds (2.8--)3--3.5 mm long…1. P. tibeticum

1b. Fruit terete, wingless, torulose, ca. 1.5 mm wide; petals 3--4 ´ 1--1.5 mm; seeds 2--2.5 mm long…2. P. wuchengyii

1. Platycraspedum tibeticum O. E. Schulz, Repert. Sp. Nov. Regni Veg. Beih. 12: 386. 1922. TYPE: China. Sichuan [as Tibet]: Tatsienlu, zwischen den Steinen des Mani auf der Passhöhe Gila, 4400 m, 4 Oct. 1914, W. Limpricht 1838 (lectotype, here designated, WRSL; isolectotype, WU).

Herbs (6--)10--20(--60) cm tall, glabrous or sparsely pubescent with trichomes to 0.8 mm long. Root fusiform, to 5 mm diam. Stem several-branched from single short base. Cauline leaves petiolate, glabrous or pubescent; petiole (0.1--)0.5--2(--3) cm long; leaf blade suborbicular to cordate or broadly ovate, (4--)7--15 ´ (1--)5--12(--15) mm, reduced in size in inflorescence, base cordate, margin repand-dentate to repand or palmately 5-lobed, the teeth or lobes not mucronate, apex obtuse. Sepals 1.5--2 ´ 0.8--1.5 mm, glabrous, margin membranous and to 0.2 mm wide; outer pair oblong, narrower than inner, not saccate at base; inner pair broadly ovate, saccate at base. Petals white, narrowly obovate to subelliptic, 4--6 ´ 2--3 mm, base cuneate, apex rounded. Filaments white, 1.1--2 mm long; outer pair slender; inner pair strongly flattened basally and 0.4--0.6 mm wide, with ovate to oblong lateral tooth 0.2--0.4 ´ 0.1--0.2 mm; anthers oblong, 0.4--0.6 mm long, apex obtuse. Ovary 6- to 9-ovuled. Fruiting pedicel slender, ascending to divaricate, straight to recurved, (3--)5--12(--20) mm long. Fruit narrowly oblong, 4-angled and longitudinally 4-winged, curved, not torulose, (6--)8--15 ´ 2.5--3 mm, base cuneate; valves glabrous, with a well-developed, winged midvein with wing to 0.5 mm wide; replum longitudinally winged with a wing to 0.5 mm; style thick, 0.5--1.5 mm; gynophore to 0.5 mm. Seeds ovate to broadly oblong, flattened, (2.8--)3--3.5 ´ 1.5--2 mm. Flowering June--August, fruiting July--September.

Alpine areas at 4100--4800 m.

Specimens examined. CHINA. Sichuan: Kanting (Tachienlu), Cheto, La, Harry Smith 11042 (MO, S, UPS); Tatsien-lu, Cunningham 124 (E); Tatsienlu (listed as Tibet), unter Gebüsch am Abstieg vom Passe Gila nach dem Haus Tajiatsuka, 4100 m, Limpricht 1667 (WRSL, WU); Dawo, Felsgrate des Ressirrma oberhalb des Passes Ssirka westlich Tschlisse tsung, 4840 m, Limpricht 1931 (WRSL). Xizang (Tibet): Batang, Yargong, Soulié 3088 (P); Tongolo, Kiala, Soulié 1024 (P).

Although Platycraspedum tibeticum was based on three syntypes, all of which were allegedly collected from eastern Tibet (Xizang), their actual localities are in Sichuan, and perhaps for that reason the species was not included in the Flora of Xizang (Kuan, 1985). However, as cited above, the species does occur in Xizang. Of the three syntypes cited by Schulz (1922), Limpricht 1838 has flowers and fruits and is herein designated as the lectotype.

The illustration of Platycraspedum tibeticum in Kuan (1987) is inaccurate in the number of marginal leaf teeth, as the species was shown to have up to eight marginal teeth when in fact the maximum it has is four. Furthermore, Ying et al. (1993) incorrectly described the lateral stamens as toothed and the median ones as linear, and the reverse is correct.

2. Platycraspedum wuchengyii Al-Shehbaz, T. Y. Cheo, L. L. Lu & G. Yang, sp. nov. TYPE: China. Xizang: Mangkang Xian, wet grounds by river, 4000 m, 27 June 1976, Qinghai-Xizang Expedition 12038 (holotype, KUN; isotype, PE).

Herba 5--25 cm alta. Radix fusiformis carnosa. Folia caulina petiolata, suborbiculata, cordata, vel subreniformia. Petala alba, subelliptica vel anguste oblonga, 3--4 ´ 1--1.5 mm. Filamenta mediana complanata, unidentata. Fructus lineares, teretes, torulosi, nonalati, 6--15 ´ ca. 1.5 mm. Semina oblonga, compressa, 2--2.5 ´ ca. 1.5 mm.

Herbs 5--25 cm tall, glabrous or sparsely pubescent with trichomes to 1 mm long. Root fusiform, fleshy, to 2 mm diam. Stem single at base, with few to several, slender, ascending to decumbent branches. Cauline leaves petiolate, glabrous or very sparsely pubescent; petiole 0.5--2.5(--4) cm long; leaf blade suborbicular to cordate or subreniform, 4--12 ´ 5--15 mm, reduced in size in inflorescence, base cordate, margin repand to shallowly and obtusely palmately 5-lobed, the lobes not mucronate, apex obtuse. Sepals 1--1.5 ´ 0.6--1 mm, glabrous, margins membranous and to 0.1 mm wide. Petals white, narrowly subelliptic to narrowly oblong, 3--4 ´ 1--1.5 mm, base cuneate, apex rounded. Filaments white, 1.1--1.5 mm long; outer pair slender; inner pair strongly flattened basally and 0.3--0.5 mm wide, with ovate to oblong lateral tooth to 0.2 ´ 0.1 mm; anthers oblong, 0.3--0.4 mm long, apex obtuse. Ovary 3- to 6-ovuled. Fruiting pedicel slender, ascending to divaricate, straight, 5--15 mm long. Fruit linear, terete, wingless, torulose, 6--15 ´ ca. 1.5 mm, base cuneate; valves sparsely and minutely puberulent, obscurely veined, wingless; replum wingless; style thick, 0.5--1.5 mm; gynophore to 1 mm. Seeds oblong, flattened, 2--2.5 ´ ca. 1.5 mm. Flowering June--August, fruiting July--August.

Wet grounds by rivers, slopes of ravines in Juniperus forests, and woods at 4000--4500 m.

Paratypes. CHINA. Sichuan: Upper Yalong basin, Chola Shan, Dege-Garze, Manigango, 31E 52N N, 99E 07N E, G. & S. Miehe & Wündisch 94-433-22 (GOET); Deige Xian, Babang Xiang, Anonymous 7389 (PE #1137899).

Platycraspedum wuchengyii is named in honor of Wu Zhengyi (Wu Chengyi), Director Emeritus of the Kunming Institute of Botany, Editor-in-Chief of the Chinese Flora Reipublicae Popularis Sinicae, and Co-chair of the Flora of China, in recognition of his outstanding contributions to the flora of China. Professor Wu annotated the holotype of P. wuchengyii as P. tibeticum.

Two collections, the type and Anonymous 7389 (PE #1137899), were cited by Wang (1993) as Platycraspedum tibeticum. It appears that the remarkable differences in the fruits of the two species (see key) were overlooked.

Acknowledgments. We are grateful to Qin Haining (PE), Sun Hang (KUN), Pete Lowry (MO at P), and W. Till (WU) for their help during visits to their herbaria. Zhu Guanghua and Song Hong are thanked for translating Chinese text and herbarium labels. We thank G. Dickoré and G. and S. Miehe (GOET) for sending to the senior author many Chinese collections for determination.

Literature Cited

Kuan, K.-C. 1985. Cruciferae. In: C. Y. Wu (editor), Fl. Xizang. 2: 323--411. Science Press, Beijing.

---. 1987. Lepidieae. In: T.-Y. Cheo (editor), Fl. Reipubl. Popularis Sin. 33: 44--109. Science Press, Beijing.

Schulz, O. E. 1922. Cruciferae. In: W. Limpricht, Botanische Reisen in den Hochgebirgen Chinas und Ost-Tibets. Repert. Sp. Nov. Regni Veg. Beih. 12: 385--390.

---. 1936. Cruciferae. In: A. Engler (editor), Die Nath rlichen Pflanzenfamilien, ed. 2, 17B: 227--658. Verlag von Wilhelm Engelmann, Leipzig.

Wang, W.-T. 1993. Cruciferae. In W.-T. Wang et al. (editors), Vascular Plants of the Hengduan Mountains. 1: 618--652. Science Press, Beijing. [In Chinese.]

Ying, T.-S., Y.-L. Zhang & D. E. Boufford. 1993. The endemic genera of seed plants of China. Science Press, Beijing.