Pinellia ARACEAE-LEMNACEAE Lemna 



above, with Arum ternatum Thunb. (1784) as the name-bringing synonym. Since citation as 

 a synonym is not valid publication (Int. Code of Bot. Nomen. 1952. Art. 46), it appears that 

 Makino, in the reference mentioned above is the first authority to validly publish the name 

 Pinellia ternata, even though he omitted mention of Tenore to whom Breitenbach credited the 

 name. Engler (Das Pflanzeur. IV. F. 222-224. 1920) also credits the combination to Breitenbach 

 without mentioning Tenore. Index Kewensis, Suppl. VI. 155 (1926) gives Pinellia ternata 

 (Thunb.) Druce in Rep. Bot. Exch. CI. Brit. Isles, 1916: 640(1917). This reference was not seen, 

 but the combination is clearly of later date than Makino's cited above. Finally, Index Kewensis, 

 Suppl. VIII. 184 (1933) gives Pinellia ternata (Thunb.) Ten. ex Breitenb., using the reference 

 first mentioned above. The present writer accepts Makino as the earliest known valid authority 

 for the combination. 



3. Pinellia pedatisecta Schott (E.P.IV.23F.224) Scapose fleshy herb, to 7dm.; fls. 

 V-VI. China; locally in Ku. Moist woods. 



182. LEMNACEAE Duckweed Family W-W& (Fu P'ing K'o) 



Monoecious scale-like floating plants lacking normal stems and Ivs., mostly pro- 

 pagating by budding of the thallus: fls. 1-3 to a thallus, without perianth; stamens 1 

 or 2; ovary 1-celled: fr. a 1-7-seeded utricle. 4 genera with about 30 species, cos- 

 mopolitan; 3 genera and 4 species in China. The simplest and some of the smallest 

 flowering plants known. 



Key to the Genera 

 Plant with rootlets. 



Plant with several rootlets; thallus 5-15-nerved, and red beneath 1. Spirodela 



Plant with a single rootlet; thallus 1-5-nerved, and green beneath 2. Lemna 



Plant without rootlets; thallus ovoid, very small 3. Wolff ia 



1. Spirodela Schleid. UWM (Fu P'ing Shu) 

 Thallus 5-15-nerved, with several vascular rootlets beneath: fls. as in Lemna. 

 Two species, cosmopolitan, except Africa; one in China. (Greek: speira, a cord and 

 dclos evident.) 



1. Spirodela polyrhiza (L.) Schleid. UW (Fu P'ing; Floating Duckweed) (G.M.385). 

 Floating; thallus with several roots. Tropical and north temperate regions; 

 locally in Che., Hup., Ku. On ponds and lakes. 



2. Lemna Linn. Duckweed aaMM (P'in Tsao Shu) 

 Thallus 1-5-nerved, with a single non- vascular rootlet beneath: fls. borne in clef ts 

 on the margin of the thallus, usually 3 in one place; two staminate, each consisting 

 of a single stamen; and one pistillate, a simple pistil. 6 species, cosmopolitan; 2 

 in China. (The Greek name of a water plant.) 



Key to the Species 

 Fronds elliptic or almost circular, 2-5 mm. across. 



Fronds symmetrical; root-sheath not appendaged; root-cap obtuse: 



seed horizontal 1 . £,. minor 



Fronds asymmetrical: root-sheath appendaged; root-cap acute: seed 



erec t 2 . L. paucicostata 



Fronds oblong-lanceolate, 5-10 mm. long 3. L. trisulca 



501 



