1928] Wexelseii: Chromosome Niimhers and Morphology in Trifolium 363 



The first statement is well illustrated by a eomparison of the 

 chromosomes in T. variegatum (fig. 1^) and T. reflexum (fig. 1/). 

 The third statement may hold as a general rule, but a rule to which 

 there are many exceptions. T. ohtusiflorum (fig. la) has 16 medium 

 to small chromosomes, T. reflexum., 16 large, but the former has the 

 largest plant size. That one must be careful in conclusions based on 

 comparisons of chromosome size in species of the same genus is also 

 brought out by the cases of intraspecific variability in shape and size 

 of chromosomes discussed below. 



Variations in Chromosome Size Within the Species 



In Trifolium, repens, two varieties were examined cytologically, 

 T. repens var. sylvestre, wild white clover, and T. repens var. gigan- 

 teum, Italian white clover or Lodi clover, three plants being studied 

 in each variety. The three plants of giganteum all had chromosomes 

 of about the same size (fig. Sa, which is a metaphase plate from a root 

 tip of plant 13a) . Of the three sylvestre plants, plant la showed very 

 small chromosomes, Ih and Ic somewhat larger, but all considerably 

 smaller than the chromosomes of 13a (fig. 3h, c, d). Karpechenko 

 (1925) studied the somatic metaphase in T. repens; he makes no state- 

 ment as to the variety used but his figure shows chromosomes of the 

 same size as those found in giganteum. Bleier (1925) and Erith (1924) 

 both studied pollen mother cells of repens. Bleier says nothing about 

 which variety was studied, Erith states that she counted giganteum, 

 hollandicum, and sylvestre, but does not say anything about differ- 

 ences in chromosome size, and it is not clear from which variety her 

 figures are taken. However, when the bivalent chromosomes in her 

 plates (1924, p. 92, x 1750) are compared with those of Bleier (1925, 

 p. 618, X 2150) it is clear that the chromosomes pictured by him are 

 at least three times as large as those of Erith. 



This case is very interesting because giganteum with the large 

 chromosomes is a giant variety, sylvestre a small variety. Erith 

 (1924) has given detailed morphological descriptions of the two 

 varieties which correspond to the plants used by the writer. The 

 length and breadth of the terminal leaflet in several plants of each 

 variety were measured and the measurements for the plants studied 

 cytologically are given below. The figures represent the average of 

 ten measurements. 



