460 
Syncotylous 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 Helianthus animus syn- 
cotyleus and in larger numbers in Mercurialis annua and 
Centranthus macrosiphon* and also occasionally in An- 
tirrhinum majns, 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. 91. 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 (Centranthus macrosi- 
phon, Mercurialis annua). Sometimes it succeeds, although 
very late, in elongating in the normal direction. In 
Helianthus annuus I have sometimes operated upon such 
1 Figured in Bcr. d. d. bot. Ges., Vol. XII, PI. IT, Figs. 3 and 4. 
