DEVELOPMENT OF PLANTS 



347 



preceding groups (Fig. 261A, 3, 4). At maturity, the two 

 sporangia on each side of the anther usually merge into one 

 cavity, owing to the breaking down of the intervening tissue. 

 The anther opens in a variety of ways, as by slits and pores, 

 permitting the scattering of the spores (Fig. 261.4, 3). The 



Fig. 26i5. Megasporophyll and megasporangia : 1, megasporophyll of 

 buttercup— s, stigma; st, style; o, ovary. 2, longitudinal section of mega- 

 sporophyll — mg, megasporangium ; in, megaspore, the mother cell having 

 formed four spores in series, but the end one only develops; i, integu- 

 ment; mi, micropyle. 



microsporophylls are often externally quite suggestive of those 

 noted in certain of the Pinales, but the megasporophylls are 

 essentially different from any other group considered, in that 

 the sporangia are inclosed in a cavity formed in the sporophyll. 

 This peculiarity is one of the important characteristics of the 

 angiosperms, as the name indicates. The megasporophyll, often 

 termed the pistil or carpel, is usually a rather elongated, flask- 

 shaped organ with a hollow swollen base and consists of a 

 stigma, style and ovary (Fig. 261B, 1) within which are pro- 

 duced the megasporangia or ovules. Such a structure would 

 result if the edges of the leaf-like megasporophylls of previous 

 groups were inrolled so as to form a closed organ. The mega- 



