GROUP V. ANGIOSPERALE : MONOCOTYLEDONES. 495 



ally two on a spike ; formula PO, A2, Gi. It. maritima is the British 

 species. 



Order 2. JUNCAGINACEJL Flowers sometimes diclinous ; both 

 perianth-whorls are sepaloid and inconspicuous ; anthers extrorse ; 

 carpels sometimes coherent ; the outer whorl of carpels is occasion- 

 ally abortive ; ovules 1-2, anatropous, embryo straight. 



Triglochin palustre, the Arrow-Grass, is common in marshes and on the 

 margin of pools : carpels coherent till mature. The monoclinous flowers 

 are disposed spirally in a long loose spike without bracts. Scheuchzeria 

 palustris is rarer ; it occurs in bogs ; the flowers are set in the axils of 

 distichous bracts : carpels free. 



Order 3. ALISMACELE. Flowers sometimes monoecious; floral 

 formula K3, CS, A3 2 + or 3, or oo, G3 + 3 or oo : perianth hetero- 

 chlamydeous ; the sepals are often coherent at the base ; the petals 



FIG. 305. Diagram of the Flower of 

 Trigloohin. 



FIG. 3C6. Flora diagrams. A of 

 Butomus. B Of Alisma. 



are white or violet ; anthers extrorse or introrse ; carpels sometimes 

 partially coherent ; ovules 1-3, campylotropous, embryo curved. 



Alisma Plantago (Water Plaintain, Fig. 306 B), has the floral formula 

 K3, C3, A3 2 +Q, GQ or more ; the numerous, monomerous, one-seeded ovaries 

 are 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. Damasonium stellatum, the Star-fruit, is found in 

 ditches in the South of England : it has two-seeded ovaries. 



Sagittaria sagittcefol.ia, the Arrowhead, has diclinous flowers with the 

 formula K3, C3, <J A oo, ? G J?. The flowers are disposed in trimerous 

 whorls, the <J in the upper and the ? in the 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 inflores- 

 cence appear above the water. 



Order 4. BUTOMACE^E. Flowers never unisexual ; general 

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

 distinct ; ovules numerous, with superficial placentation ; embryo 

 straight or ciirved. 



