and Laboratory Methods. 1411 



CURRENT BOTANICAL LITERATURE. 



Charles J. Chamberlain. 



Books for review and separates of papers on botanical subjects should be sent to 



Charles J. Chamberlain, University of Chicago, 



Chicago, 111. 



REVIEWS. 



Guignard, L. La Double Fertilization dans Double fertilization in Zea mays, which 

 leMais. Jour.duBot. 15: 1-14, 1901- j^^g ^een suspected for some time, 



and which is believed to be the cause of the phenomenon known as xenia, is 

 described in a recent paper by Guignard. 



The mature pollen grain contains, besides the vegetative nucleus, two very 

 small elongated generative cells, each in the form of a slender rod, curved or 

 straight. The ends are often pointed. The protoplasm of these cells is much 

 reduced and difficult to distinguish. Their nuclei appear almost homogeneous. 



The two synergids and the oosphere are large. The pyramidal synergids 

 occupy the summit of the sac, and in many cases have a large vacuole in the 

 base. They show near the tip a conspicuous longitudinal striation, especially in 

 material fixed in absolute alcohol. Their nuclei do not stain readily at the 

 time of fertilization. 



The nucleus of the oosphere is very large and contains much chromatin. 

 The protoplasm surrounding the nucleus is, ordinarily, highly granular and 

 much massed together at the time of fertilization. 



Near the oosphere, sometimes in the median line of the embryo-sac, some- 

 times at one side, are the two polar nuclei. These nuclei do not fuse before 

 fertilization. They have each a relatively large nucleus and small amount of 

 chromatin. 



As many as a dozen multi-nuclfeate cells may be found in the much narrowed 

 antipodal end of the embryo-sac. 



The pollen tube, after penetrating the embryo-sac, usually seems to dis- 

 charge its contents into one of the synergids. In one instance the two elongated 

 male nuclei were observed resting against the base of a synergid ; under high 

 magnification their chromatin was distinct. One of the male cells unites with 

 the oosphere, the other with the polar nuclei. These nuclei are bound together 

 by the last male cell. Fertilization proceeds with such great rapidity that it 

 could be observed in very few preparations. In general, the ovules at the base 

 of the ear are first fertilized. 



In hybrids many ovules are not fertilized. 



After fertilization, one of the synergids usually persists for a time, with its 

 contents finely granular and refractive. Division of the fertilized polar nuclei 

 proceeds with such rapidity that the course of cell-division could not be fol- 

 lowed. The first two nuclei of the endosperm are large, each one having an 

 enormous nucleolus and many smaller nucleoli. 



It is to be regretted no figures are given. W. J. G. Land. 



Chicago. 



