MALE CELLS 453 



plants and its relation to the course of meiosis is shown by Artemisia 

 nitida (Table 68). 



(ii) Meiosis in Non-Functional Cells. The mother-cells of male 

 spores and male gametes of apomictic plants and animals (where 

 they are formed) show various kinds of behaviour which cannot be 

 predicted merely from a knowledge of the behaviour in the functional 

 cells on the female side. They have been studied more thoroughly 

 than the functional cells and provide valuable evidence of the 

 origin of apomixis. 



In sexually reproducing organisms where a failure of pairing 

 depends merely on mechanical chromosome relationships {i.e., 

 structural differences, numerical inequality among the pairing 

 chromosomes, or their excessive number as in autopolyploids) we 

 find a correlation between the conduct of meiosis in the male and 

 female cells. The evidence of this correlation consists in the 

 similar fertility of structural hybrids on male and female sides, 

 and of the similar character of their offspring from male and female 

 cells. The same correlation applies to many of the genotypically 

 controlled abnormalities of meiosis, but it does not apply to all of 

 them. There are many cases of such an abnormality specifically 

 affecting either the male or the female cells of hermaphrodites. 

 If we wish to know how far the conduct of parthenogenetic meiosis 

 depends upon mechanical properties of chromosomes and how far 

 on a genotypic property we must find out how far this correlation 

 applies. 



All facultatively apomictic plants have normal or fairly normal 

 meiosis in the pollen mother-cells, e.g., Alchemilla speciosa (Murbeck, 

 1902), Thalictrum purpurascens (Overton, 1904), Hieracium 

 aurantiacum (Rosenberg, 1917), Elatostema acuminatum (Strasburger, 

 1910). In this species the pollen degenerates afterwards, as in so 

 many male-sterile plants. Otherwise they are able to produce 

 gametes with a normally reduced chromosome number. 



In some organisms which are obligatorily parthenogenetic the 

 male cells function in stimulating parthenogenesis ; their meiosis is 

 then fairly regular. In Zephyranthes texana it is entirely so, and 

 the pollen actually functions in fertilising the endosperm nucleus. 

 Moderate or even high pollen fertility is sometimes found in the 



