CHAPTER 2 



THE MICROSPORANGIUM 



In considering the course of events leading to the origin of the 

 embryo, we must first deal with the development of the micro- and 

 megasporangia. It is the microsporangium which produces the mi- 

 crospores and eventually the male gametophyte. Similarly, the 

 megasporangium, or ovule, is the place of formation of the mega- 

 spores and the female gametophyte. The latter, after fertilization, 



Fig. 23. T.s. anther of Lilium philadelphicum, showing dissolution of cells sepa- 

 rating the two microsporangia on each side. Note the fibrous endothecium and 

 stomium s. The minute punctate markings lining the inner wall of the anther 

 probably represent remnants of tapetum. (After Coulter and Chamberlain, 1903.) 



produces the embryo and endosperm, while the entire megasporan- 

 gium with its enclosed structures becomes the seed and the progen- 

 itor of the next generation. 



A typical anther comprises four elongated microsporangia, but 

 at maturity the two sporangia of each side become confluent owing 

 to the breaking down of the partition between them (Fig. 23). A 

 cross section of a very young anther shows a mass of homogeneous 

 meristematic cells surrounded by the epidermis (Fig. 24 A, B). It 



28 



