BOT— Vol. I. ] CA NNON—A VENA FA TUA . 



341 



observed in the family which is probably the nearest ally of 

 the grasses, viz. the Sparganiaceas, and in the Aracese.^ 



The antipodal nuclei of the oat begin to divide as soon as 

 the lower polar nucleus is separated from them. They 

 divide repeatedly and each nucleus becomes enclosed in 

 a globular mass of protoplasm. The increase in number 

 is accompanied by an increase in the size of the cells and 

 also of their nuclei. A good idea of this growth of the 

 antipodal complex may be had by comparing figures 22, 

 23 and 25. The multiplication of the antipodals and their 

 increase in size takes place at the expense of the nucellus 

 (cf. figs. 23 and 25). The greatest number of antipodals 

 is found at the time of the fertilization of the egg. This 

 number was not exactly determined, but it was at least 36, 

 which corresponds with that given by Koernicke for the 

 wheat. There is uniformly in Avena as in Tritiaim one 

 nucleus in each cell. Fischer describes three antipodal 

 cells only for Alopecurus and Sesleria, but says that there 

 are four nuclei in each. Melica, on the other hand, does 

 not show multiplication of the antipodals in any way. When 

 they begin to divide, the antipodal cells of Avena occupy a 

 position near, but not in, the chalaza end of the embryo-sac, 

 and a fine drawn through the long axis of the embryo-sac 

 would bisect them. As the embryo-sac develops, the anti- 

 podals assume a lateral position and retain it until they 

 disappear. 



The antipodal complex shows, in section, a characteristic 

 crescent form; the nuclei are large and stain deeply with the 

 common staining agents. No vacuoles are visible in the 

 young antipodal cells, but they appear as the cells grow, 

 and are increasingly marked during their dissolution. 



The disorganization of the antipodals begins simulta- 

 neously with the formation of the endosperm, and usually 

 they can no longer be seen at the time when the micropylar 

 end of the embryo-sac is being filled with endosperm. Fig- 

 ure 27 shows the condition of the antipodals when the endo- 

 sperm is beginning to form. A few large vacuoles in each 



1 Campbell, Bot. Gaz., March, 1899, and Proc. Cal. Acad. Sciences, 1899. 



