492 
STRUCTURE AND LIFE HISTORIES 
(Alisma Plantago-aquatica) . Like the cat-tails, the water- 
plantains are marsh herbs (Fig. 377), with flowers either 
perfect, monoecious or dioecious; in Alisma they are per- 
fect, with usually six stamens. The three sepals are per- 
sistent, but the three white petals are deciduous (i.e., falling 
s.f 
FIG. 376. Cat-tail (Typha latifolia). A, longitudinal section of 
portion of inflorescence; Sp, spadix; p.f., pistillate flowers; s.f., staminate 
flowers. B, pistillate flower, greatly magnified; ov, ovary; sly, style; stig., 
stigma; sc, sterile hair; P, pollen grains, in characteristic groups of four 
each. (Cf. Fig. 375.) 
away early). The numerous ovaries are borne in a circle 
on a flattened receptacle. The possession of calyx and 
corolla, together with other features, mark the family as 
more highly organized than the cat-tails. 
429. Grass Family (Gramineae). The grasses consti- 
tute one of the largest, one of the most important econom- 
ically, and one of the most difficult taxonomically, of all 
