140 



ELEMENTARY STUDIES IN BOTANY 



In the compound (syncarpous) pistil there are two dif- 

 ferent conditions of the ovary that must be mentioned. In 

 the one case, the carpels are arranged so as to inclose a single 

 cavity, as if open carpels had united edge to edge (Fig. Ill, 

 A). In the other case, the carpels are arranged so that 

 there are as many cavities as there are carpels, as if closed 

 carpels had come together, each with its own cavity (Fig. 

 Ill, B). These cavities within the ovary were long ago 

 called " cells," and the inappropriateness of the term is 

 evident. Therefore, some ovaries are said to be one-celled 



FIG. 112. Sections of ovules, showing outer (oi) and inner (ii) integuments, micro- 

 pyle (m), nucellus (n), and megaspore (em) ; in B the ovule is curved, and in C the 

 stalk is curved, so that in both cases the micropyle h turned towards the wall of 

 the ovary. 



and some are two- or more-celled. It must be noticed that 

 this does not correspond necessarily to the number of carpels, 

 for although a simple pistil has a one-celled ovary, a com- 

 pound (syncarpous) pistil may have either a one-celled ovary 

 or a several-celled ovary. 



84. The ovule. The structure of the angiosperm ovule 

 is essentially the same as that of the gymnosperm ovule. 

 That is, there are one or two integuments investing the nu- 

 cellus, whose tip is exposed at the micropyle (Fig. 112). 

 In the midst of the nucellus the usually solitary megaspore 

 appears, for, as in Gymnosperms, although several . mega- 

 spores start, it is seldom that more than one develops to the 

 full size and power. 



