204 



BOTANY 



PART I 



the vegetative cells of the other without change in the number of chromosomes. 

 In Athyrium filixfoemina clarissima, Jones, the fern plant arises without nuclear 

 fusion from vegetative prothallial cells with diploid nuclei ; without any production 

 of spores, or the occurrence of a reduction division, the diploid cells of the leaf 

 margin produce diploid prothallia (APOSPORY). According to YAMANOUCHI (in 

 Nephr odium molle) a haploid prothallial cell may, without nuclear fusion, give rise 



FIG 233.-Pollen.mother.cell of a -Lily in division, somewhat diagrammatic. Fixed with chrom- 

 atic acid and stained with iron haematoxylin. The chromatophores are not visible 1 The 

 f the chromosomes. Further description in text. (After STRASBURGER.) 



to a haploid fern-plant. Further, it is possible to obtain experimentally, on the 

 regeneration f cut portions of the stalks of moss capsules, a diploid moss plant 

 i.e. a diploid gametophyte ; this produces diploid sexual cells that are capable of 

 fertilisation. Tetraploid moss capsules are the result, and from these again by 

 regeneration tetraploid moss plants have been obtained. It is evident, therefore, 

 that there is not a direct connection between the chromosome number and the 

 construction of the two generations ( 95 ). 



In some plants the reduction division is omitted so that diploid egg-cells are 



