344 University of California Publications in Agricultural Sciences ["Vol.2 



Figure B was made up from an examination of the whole root and 

 shows that the tetraploid area occupied the major portion of the root 

 and that its cross-section was very irregular in shape. The dotted 

 lines indicate the portions of the boundary between the 2?i and 4n 

 areas which could not be accurately determined. It is uncertain 

 whether the tetraploid area extended into the central cylinder or not. 

 The tetraploid area at a is two cell layers deep, at h it is only one, but 

 opposite a at c it occupies most or all of the cortex. While there is 

 considerable variation in cell size within both areas the average size 

 of the tetraploid cells is larger than that of the diploid. 



>» 



a^ 



^ki^Jf* 



Fig. A. 1, Diploid chromosome complex of hiennis-setosa hybrid derivative 

 (271 = 24). 2, Tetraploid complex (2u = 48) from chimeral root of the same 

 plant. 



The shape of the tetraploid area is of some interest from the point 

 of view of development as presumably the doubling of chromosomes 

 took place in one of the initial cells from which the root developed. 

 The area does not show the comparative regularity in shape exhibited 

 by Nawaschin 's tetraploid sector. On the other hand, tetraploidy here 

 is confined to one definite area, which was not the ca.se with Lesley's 

 (1925) tomato chimeras, where isolated areas of tetraploid cells were 

 obsei'\'ed. The condition is similar to that which Langlet (1927) 

 found in two roots of ThaUctrum but differs from that reported by 

 Winge (1927) in Tragopogon hybrids where the tetraploid parts of 

 two roots by reason of their larger cells rendered the cross-sections 

 of the roots eccentric. Tlie plant bearing this chimeral root was of 

 normal appearance in the rosette stage but unfortunately died before 

 flowering. 



The second ca.se showing a chimeral condition was a plant of 

 Crepis Bureniana (7^ = 4). Of the thirty roots of tliis plant which 

 were examined two were tetraploid, having 16 chromosomes in all the 



