REPRODUCTION AND DISPERSAL 



865 



mum) both the open and the closed flowers are aerial, the former being 

 large and showy, while the latter appear later and are much smaller. 

 In Leersia oryzoides, the conspicuous open monoclinous flowers rarely 

 fruit, though the cleistogamous flowers hidden within the leaf sheaths 

 are fertile. Few if any species have exclusively cleistogamous flowers, 



though this condition has been reported 

 for Myrmecodia echinata, Salvia cleis- 

 togama, Ophrys apifera, Ammannia 

 latifolia, and several grasses. 



The cleistogamous and chasmoga- 

 mous flowers of the same species differ 

 widely in structure, though they agree 

 in some important respects, as in the 

 potency of own pollen. In general thj 

 former are much the smaller, and in 

 some respects they resemble early 

 stages in the development of the latter; 

 this is especially true as to the corolla, 

 which either is entirely lacking or exists 

 in the form of protuberances (e.g. in 

 Spec til aria), as in the bud of a chas- 

 mogamous flower. The development 

 of the stamen and pistil is not arrested, 

 as is that of the corolla, though the 

 stamens may 

 be fewer in 

 number, and 

 usually the 



pollen grains are much less numerous 

 than in chasmogamous flowers. In 

 Helianthemum the closed flowers have 

 but three to ten stamens, as contrasted 

 with the numerous stamens of the open 

 flowers; sometimes the stamens are 

 reduced to a single anther, and the pol- 

 len grains may number only a dozen 

 or even less in each chamber (as in 

 OxaUs). Occasionally the pistil exhibits reduction; for example, in 

 Helianthemum the open flowers have many ovules, while there are only 



FIG. 1191. Fruiting shoots of 

 Poly gala polygama ; the aerial stem (a) 

 bears showy racemed flowers which 

 open and may be cross pollinated; on 

 underground stems (M) are borne 

 numerous cleistogamous flowers (/), 

 which are close pollinated and give 

 rise to abundant seed pods (p). 



