304 ALLEN— SEX INHERITANCE IN SPH.^ROCARPOS. 



developing sporophyte. Those which have been seen show that 

 about sixteen chromosomes are present and that one and only one 

 of' the group is much larger than the others, being, therefore, ob- 

 viously derived from the female parent. Fig. 22 represents the 

 two anaphase groups in a dividing cell of a young sporophyte ; each 

 group shows fifteen chromosomes, one of which is the large one. 

 The sixteenth chromosome which would be expected to appear in 



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Fig. 22. Two anaphase chromosome groups in a dividing cell of a young 

 sporophyte ; A, the group seen at an upper, B, that seen at a lower, focus ; 

 X, the large chromosome. X 3800. 



each of these groups is, it seems likely, the small element derived 

 from the male parent, which here is not seen either because of its 

 too light stain or because it is hidden by one of the others. 



The first division of the spore mother cell nucleus (the hetero- 

 typic division) has not yet been seen; but a considerable number of 

 spore mother cells have been found in which the second (homoeo- 

 typic) division was in progress. In every one of these latter cases 

 in which the complete series of sections of a spore mother cell was 

 present, one of the two spindles in the cell bore a large chromosome, 

 and the other did not. Figs. 23 and 24 show polar views of the two 

 homoeotypic metaphase groups in a single spore mother cell ; in the 

 group of Fig. 24 a large chromosome (apparently longitudinally 

 split) is present; the group of Fig. 23 includes no large chromo- 

 some. An exact count of the smaller chromosomes has not been 

 found possible at this stage because of the irregularities in their 

 shape and distribution. The fact that a single group is commonly 

 represented in several sections (those chosen for Figs. 23 and 24 

 are unusually favorable in this respect) involves additional diffi- 

 culties. 



The conclusion seems warranted, from the presence of a large 



