SPERMATOPHYTES— ANGIOSPERMS 



367 



variably show a difference in staining capacity when the male nuclei 

 are just discharged from the pollen tube. With cyanin and erythrosin, 

 the male nucleus stains blue and the female, red; hence the obsolete 

 terms "cyanophilous" and "erythrophilous." With safranin, gentian 

 violet, orange, the egg nucleus stains more with safranin and the male 

 with gentian violet; but as the two nuclei come into contact within the 

 egg, they begin to stain alike, 

 the male nucleus staining 

 more and more like the fe- 

 male. As fertilization pro- 

 gresses, it becomes difficult 

 or, at present, impossible to 

 distinguish any difference be- 

 tween the two nuclei. The 

 male nucleus which takes 

 part in the "triple fusion" 

 to form the endosperm nucle- 

 us behaves in the same way. 



Lilium is a very good and 

 always available type for illus- 

 trating fertiHzation (Fig. 134). 

 Take ovaries from flowers 

 whose petals have withered 

 but have not yet fallen off. 

 Though their embryo sacs 

 and nuclei are smaller, Sil- 

 phium and Helianthus are 

 good types, because their 



curved or twisted male nuclei are easily distinguished from the 

 spherical nuclei in the embryo sac. The embryo sacs of orchids are 

 very small, but ovules are extremely numerous and the chances for 

 securing the fusion of nuclei are correspondingly good. In Cijpripedi- 

 um the nuclei do not fuse in the resting condition, but the chromo- 

 somes of the two parents are perfectly distinct in the egg. The general 

 statement that nuclei fuse in the "resting condition" is not correct, and 

 probably the chromosomes of the two gametes never fuse. 



The endosperm. — Some of the preparations intended for fertiliza- 

 tion will be likely to show early stages in the development of endo- 

 sperm. 



Fig. 134. — Lilium philadelphicum: photomicro- 

 graph of section showing fertiUzation and also the 

 triple fusion; from a preparation and negative by Dr. 

 W.J. G. Land. Xo85. 



