346 University of California PnhJications in Agricultural Sciences [Vol.2 



the cortex, mostly near the peripheiy, and in one region a group of 

 them seems to be responsible for the somewhat misshapen appearance 

 of the root in cross-section (pi. 55 a,c). The cells vary in size, some- 

 times extending through three or four sections T/x thick. They are 

 more or less vacuolated, depending on their size, but even the smallest 

 ones could be distinguished almost at a glance by their less densely 

 staining cytoplasm. 



The normal chromosome complex of 8 was to be seen in several 

 plates of normal cells. In one very large vacuolated cell a large 

 number of chromosomes was observed, apparently in metaphase 

 (pi. 55 d). Note the V-shaped arrangement of the metaphase plate. 

 The chromosomes could be seen in 3 successive sections of 7/i, thickness. 



Nawaschin (1926) has reported a giant cell with over 500 chromo- 

 somes in a root tip of Crepis tectorum and takes up favorably the 

 theory that it has arisen by successive chromosome divisions without 

 accompanj'ing cell divisions. The cell he shows is not greatly unlike 

 some of those seen in this material. Here, however, there seems to be 

 some evidence that the large cells are the result of fusion of several 

 smaller ones. The V-shape of the one plate observed in a giant cell 

 indicates that it may be a combination of two plates and that a nuclear 

 fusion has taken place. Plate 55 c gives the impression that two large 

 cells are in the process of fusion and indeed the cell wall has practic- 

 ally disappeared. It seems likely that such cell fusion might be asso- 

 ciated with an abnormal or pathological condition of the root, further 

 evidence of which was to be seen in small black areas probably repre- 

 senting degenerated cells (pi. 55/;). 



The origin of tetraploidy in diploid tissue has been discussed by 

 various investigators. In some cases it has been associated with specific 

 outside influences. The effect of narcotics in inducing tetraploidy has 

 been investigated by Nemec (1903) and Sakamura (1920). Blakeslee 

 and Belling (1924) found tetraploid shoots in Datura plants subjected 

 to cold. Lesley (1926) found tetraploid areas in tomato plants 

 affected by mosaic and thought it might be possible that local changes 

 due to this disease might affect mitotic processes. Cases of polyploid 

 cells have been attributed to abnormal processes related to degenera- 

 tion as in the investing cells of the ovaries of Anasa tnstis (Wilson, 

 1906). Tlie doubling of chromosome numbers in Winkler's (1916) 

 well-known chimeras has been attributed to the effect of wounding. 

 Jorgensen and Crane (1927) have recently secured tetraploidy in 

 Solanum by the use of Winkler's method. Winge (1927) finds that 



