GROUP IV. — PHANEROGAMIA : ANGIOSPERMJ: : MONOCOTYLEDONES. 555 



crowded on the broad receptacle. The main axis of the inflorescence bears 

 whorls of branches which have a helicoid ramification. It is rather common in 

 damp spots. Damasoninm stellatum, the Star-fruit, is found in ditches in the 

 South of England : it has two-seeded ovaries. 



Sagittaria sagittipjolia, the Arrowhead, has monoecious flowers with tbe 

 formula A^3, C3, <J J[ oo, ? G^. The flowers are disposed in trimerons whorls, 

 the cJ in the upper and the ? in tbe lower whorls. The anthers are extrorse. 

 The ovaries, which are very, numerous and one-seeded, are inserted on a fleshy 

 receptacle. Only the sagittate leaves and the inflorescence appear above the 

 water. 



Order 4. Bctomace^. Flo vs^ers never monosporangiate; general 

 floral formula the same as in Alismacea3; anthers introrse ; carpels 

 distinct ; ovules numerous, with superficial placentation ; embryo 

 straight or curved. 



Butnmus umbellatus is 

 the Flowering Rush (Figs. 

 360 A, 361). The flowers, 

 which have violet petals, 

 have the following for- 

 mula : 7v3, C3, ^3.2 + 3, 

 G^+i?; they are arranged 

 in an umbellate helicoid 

 cyme at the apex of the 

 scape, which is about 3 

 feet high ; this and the 

 leaves, which are of about 

 the same length, spring 

 from an underground rhi- 

 zome. The ovules, which 

 are numerous, are borne 

 on the inner surface of 

 the carpels (Fig. 338 C) : 

 the embryo is straight. 



The other genera all 

 have a curved embryo : in 

 Tenagocharis (Butomopsis) there are nine stamens and six carpels: in Hydro 

 cleis there are indefinite stamens (some sterile) and six carpels : in Limnoch^ri^ 

 both the stamens (some starile) and carpels are indefinite. 



Fig. 361. — Butomus umbellatus. A Flower (nat. size). 

 D Gynaeceura (mag.); n stigmata. / Diagram: p p 

 perianth; /stamens of the outer whorl duplicate: /' 

 stamens of the inner whorl; c outer, and c' inner whorl 

 of carpels. (After Sachs.) 



Cohort 1 

 seeds with starchy endosperm 



Sub-series. SyiwarpcR. 

 Gynaeceum syncarpous. 

 Commelynales. Perianth 



hetorochlamydeous ; 



Order 1. Xyridace^. Herbaceous sedge-like plants ; floral 



