CYTOLOGICAL STUDIES OX CEREALS AND THEIR HYBRIDS. 



170 



chromosomes. On the other hand, Schaffner, Dixon, etc. proposed that the double chro- 

 mosomes arise through looping/" Farmer and Moore ('03) published a treatise supporting 



('05, '09), Strasburger ('05) Miyake ('05) Overton ('05), etc.. Recently, Yamanouehi ('09) 

 in Fucus, Hyde ('09) in Hyacinthus and Mottier ('07, '09) in Lilium confirmed the loop- 

 theory; while Gates ('08), Geerts ('09) and Davis ('09) in Oenothera, and Schaffner ('09) 

 in Agave are on the side of Farmer and Moore's theory. Some authors, for instance, 

 Montgomery ('98), Yamanouehi ('09, '10), and Gates ('09) believe that two modes of 

 formation of the double chromosomes— the looping and separation— exist in the plant 

 kingdom. 



I studied this point with great care, tracing the process thoroughly; and I am fully 

 convinced, that the separation-theory is correct, at least, in the case of cereals used in my 

 study. In barley I was able to confirm this point most easily and plainly, as is to be 

 seen in Fig. 20 and 21 of PI. X. The process in wheat and rye, although not so plain 

 as in barley, is still easily traced (PI. XI, Fig. 43, 44, 66, 64). 



