460 



Syncotyloiis Races. 



according- to the breadth of the cotyledons on the normal 

 plant. I found instances of these remarkable and pretty 

 structures almost every year in HeliantJms annuus syii- 

 cotylcus and in larger numbers in Mercurialis annua and 

 Ccntvanthns macrosiphon,^ and also occasionally in An- 

 tirrhinum majus, Sinapis alba, etc. 



The fusion of these cotyledons sometimes results in 

 a pressure being exerted on the plumule and interfering 

 with its growth, and we often find that syncotyls grow 

 slower than normal seedlings, at least at first, and that 



Fig. QT. Raphanus Raphanistrum. A cotyl pitcher ex- 

 panded in the form of a disc. A, from the side ; B, the 

 same, seen obliquely from above and showing the plumule. 



amphi-syncotyls are especially backward. The extent of 

 this influence cannot, as yet, be measured ; but the fact 

 that syncotyls are so much rarer than tricotyls may per- 

 haps be explained by this check on their growth. Some- 

 times the plumule breaks sideways through the cotyl- 

 pitcher by splitting its lower part (Cenfranfhus macrosi- 

 phon, Mercurialis annua) . Sometimes it succeeds, although 

 very late, in elongating in the normal direction. In 

 Helianfhus annuus I have sometimes operated upon such 

 ' Figured in Bcr. d. d. hot. Ges., Vol. XTT, PI. TT, Figs. 3 and 4. 



