CONIFERALES 



339 



In a form with short, thick chromosomes, at early metaphase of 

 the first division in the fertihzed egg, it would be easy to count only 

 the X number of chromosomes; but each of such chromosomes would 

 really be quadrivalent, and in the anaphase the 2x number would 

 appear. 



This is the only account of such a behavior of chromosomes at 

 fertilization in any gymnosperm, although Hutchinson believes 

 that my own figures and especially Dr. Margaret Ferguson's"'^ 



f. 



Co 



hPil^ 



Fig. 329. — Abies balsamea: diagrams shov/ing the behavior of the chromosomes at 

 fertihzation and at the first mitosis of the fertihzed egg. The chromosomes of the egg 

 nucleus are shown in black; those of the sperm, in outUne. Only two of the sixteen 

 chromosomes of each gamete are shown. — After Hutchinson.^" 



more detailed drawings, are better interpreted according to his dia- 

 gram. 



In Puccinia graminis the two gamete nuclei appear at the begin- 

 ning of the aecium and divide in pairs throughout the aecium stage 

 and through the urediniospore and teliospore stages, coming to- 

 gether under one membrane only at the close of the teliospore stage. 

 In the crustacean, Cyclops, the two gamete nuclei also divide in 

 pairs throughout a lesser part of the life-history before they come 

 together under one nuclear membrane. In Ahies the chromosomes 

 of the gamete nuclei are distinct after the two groups of chromo- 

 somes are included within a single nuclear membrane. Then there 

 is a pairing of male and female chromosomes. That such a pairing 

 takes place at the reduction division, every cytologist has observed. 

 In Ahies such a pairing also takes place at the reduction division. 

 Whether such a pairing as Hutchinson described for Abies may not 

 be general is at least worth a careful study. It should be noted that 

 the chromosomes in Ahies halsamea are large and much more favor- 

 able for study than those of Pinus or Juniperus. 



