No. 526] SEXUAL REPRODUCTION IN ANGIO SPERMS 607 



fest themselves in the progeny with varying degrees of 

 intensity, or in such combinations that entirely new 

 marks or characters may appear; consequently char- 

 acters are spoken of as dominant, recessive, latent, etc., 

 and it not infrequently happens that estimates are placed 

 upon absent characters. All of this implies that these 

 external marks of living things are the manifestations 

 of the activities of certain parts of the living substance, 

 which are in competition, or among which there is an 

 unceasing struggle. Attempts are also made to predict, 

 by means of mathematical formula?— and with surprising- 

 success in some cases — which of these forces or activities 

 will gain the upper hand and dominate, and which will 

 be secondary. Furthermore, sexual reproduction in 

 phanerogams always implies a something that we know 

 as maleness and femaleness, and this maleness and fe- 

 maleness are phenomena which distinctively characterize 

 the gametophytes. Maleness and femaleness may, in 

 certain cases, give a distinctive mark to the sporophyte, 

 as in dioecious plants, if we admit that such a thing as 

 an absolutely dioecious sporophyte exists in angio- 

 sperms. But male and female marks are first mani- 

 fested in the sporophyte of most seed plants by the pro- 

 duction of the pollen and of the megaspores, which pro- 

 duction is, of course, a matter of heredity. In the forma- 

 tion of pollen, it is well known that it is the nucleus which 

 undergoes the important and complicated changes in 

 division; the cytoplasm, so far as present knowledge ex- 

 tends, is halved arbitrarily. The same is likewise true 

 in the development of the megaspores. In the case of 



by which, as experimental evidence seems to imlicate! 

 different intensities of maleness and femaleness pass 

 respectively to the several resulting cells. Both male 



grow under similar environmental conditions, namely, 

 that of a parasitic habit within living tissue. The 

 sperms of the pollen tube consist mainly of nuclei, with 

 scarcely any distinctive characteristics in the scanty 



