THE ANGIOSPERMAE 



1443 



fertilizing nuclei. This division may occur, as we have already seen, in the 

 pollen grain, forming a trinucleate grain. Mitosis then seems to follow a 

 normal course, with nothing peculiar about it. Division of the generative 

 cell follows mitosis, either by means of a cell plate, or by constriction, or 

 by a mixture of both processes. Two complete, uninucleate cells are thus 

 formed, and in this condition they enter the pollen tube. The sperm cells, 

 as we may now call them, often have long tails of finely vacuolated cyto- 

 plasm (Fig. 1323), and in the tube they may become drawn out to a remark- 

 able length. 



There are many other cases in which the division of the generative cell 

 happens in the pollen tube and these divisions show peculiarities which have 

 engaged much attention. For one thing they seldom show a visible spindle 

 or metaphase plate and the chromosomal figures are distorted, apparently 

 by the confined space in w^hich division occurs (Fig. 1324). It is curious, 





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Fig. 1324. — Comallaria jnajalis. A-D, IVIetaphase, anaphase and telophase in 

 division of the generative nucleus. E, Naked generative nuclei after 

 division, in the protoplasm of the pollen tube. F, Hetuerocallis flava. 

 Generative cells each with its own cytoplasm. {After Traukovsky.) 



