302 



ALLEN— SEX INHERITANCE IN SPHyEROCARPOS. 



the chromosomes in favorable positions to make such identification 

 reasonably certain. However, in all of the numerous division fig- 

 ures that have been seen in various parts of female plants the single 

 large chromosome is present and conspicuous. 



The chromosome groups of the male contain no element at all 

 like the large chromosome of the female. Seven of the chromo- 

 somes of the male, varying in length among themselves, seem to cor- 

 respond to the seven smaller ones of the female. The eighth chro- 



FiG. i6. A group of cells from a developing antheridium ; nuclei in late 

 prophase ; y, y, the small chromosome. X 3800. 



mosome (3', Figs. 14, 15, 16) is very small. This small chromosome 

 is not always easily distinguishable. In the group shown in Fig. 14, 

 for instance, the body y is very lightly stained ; the same is true of 

 the body similarly identified in cell A, Fig. 16. However, in the 

 majority of cases, as in cells B, C, D, and E, Fig. 16, and in the cell 

 shown in Fig. 15, in which the chromosomes are unusually widely 

 scattered, this small element is stained like the other chromosomes 

 and is plainly one of them. It appears certain, therefore, that a 

 very small chromosome in the male in some way corresponds to, or 

 replaces, the very large one of the female. 



Figs. 17 to 21 show stages in the division and separation of the 

 chromosomes in dividing cells of the female. In the cell represented 

 in Fig. 17 the chromosomes or most of them, including the large 

 one, are longitudinally split. Figs. 18 to 20 illustrate a peculiarity 

 in the behavior of the large chromosome — namely, that its daughter 



