476 



NAT DEAL HISTOBY OF PLANTS. 



IV. TRAPA SEEIES. 



The flowers of Trapa' (fig. 453-456) are hermaplirodite and 

 tetramerous. The receptacle has the form of a shallow cup, in which 

 is inserted the base of the ovary, whilst its upper portion is free. 

 The perianth and androecium are, consequently, inserted perigynously 



Trapa natans. 



Fig. 453. Flower 

 without corolla. 



Fig. 454. Diagram. 



Fig. 465. Long. sect, of flower. Fig. 456. Fruit. 



on the margin of the receptacular cup. The calyx is composed of 

 four sepals, two of which are lateral, one anterior and one posterior, 

 valvate or slightly covered at the margin by the preceding. Four 

 sessile petals alternate with the sepals, imbricate and crumpled ^ in 

 the bud. The stamens, inserted with the petals, outside a thick, 

 crenelate or undulate perigynous disk, are four in number, superposed 

 to the sepals, and formed each of a free subulate fi.lament, and a 

 bilocular anther, dehiscing introrsely or marginally.^ The ovary, in 

 great part superior, is of two lateral cells, surmounted by a style 



can type still imperfectly known, Heisenbachia 

 Presl {Sel. SfiBnIc. ii. 36, t. 54), considered as a 

 distinct genua by Endlichek {Gen. n. 6127) and 

 by Bentham and Hooker (Gen. 762, n. 14), 

 and which, appears to differ from Zopezia only 

 in the absence of a coroUa, if the analysis of 

 Presl is correct. 



1 Trapa L. Gen. n. 157. — Adams. Fam. des PI. 

 Ji_ 84.— J. Gen. 68. — GiEHTN. Fruet. i. 127, t. 26. 

 — Lamk. III. t. 75.— Desrx. Diet. iii. 669. — 

 TuRP. Diet. So. Nat. Atl. t. 219.— DC. Frodr. iii. 



63. — Nees, Gm, ii. t. 5. — Spaoh, Suit, d Buffon, 

 iv. 443. — Endl. Gen. n. 6140. — BARNfeoDD, Ann. 

 So. Nat. ser. 3, ix. 222, t. 12-15.— Payee, Org. 

 455, t. 106.— B. H. Gen. 793, n. 21.— H. Bn. 

 Fayer Fam, Nat. 378 ; Adansonia, xii. 24. — 

 Hook. Fl. Ind. ii. 590. — Tribuloides T. Inst. 565, 

 t. 431. — Shringata Jones, As. Res. ii. 350; iv. 

 253. 



^ It is sometimes twisted. 



' Pollen dry, eUiptioal ; in water, trigonal, 

 like that of the (Enothereai. (Bahneoxjd.) 



