POLYPLOID SERIES 171 



3 chromosomes, but 3 long, 4 medium, and 2 short chro- 

 mosomes ; that C. ericetorum does not contain 5 such 

 sets, but 1 medium and 14 short chromosomes, and that, 

 consequently, the chromosome groups in these two spe- 

 cies have not arisen through an addition of such sets but 

 in some other way. ' ' More problematical polyploid series 

 are reported in Rumex, Papaver, Callitriche, Viola, Cam- 

 panula, Lactuca. Two numbers, one of which is double or 

 triple the other, have been found in Plantago (6, 12), 

 Atriplex (9, 18), Drosera (10, 20), Platanthera (21, 63). 

 It has also been recently reported by Longley that haw- 

 thorns and raspberries, known to be complex polymor- 

 phic species, show extensive polyploidy. 



