Tricotyly and the Amuigciiicfit of Leaves. 371 



toDk place before the cotyledons were dead. \\\ Dipsaeiis 

 syl-i'esfris tors its, a race which is usually ricli in lernar\- 

 in(h\ iduals, these are almost without exception decussate 

 in early youth. 



On the boundary between the 2- and 3-merous whorls 

 2!/2-nierous ones not infrequently occur. I mean whorls 

 with one normal and one more or less deeply cleft leaf. 

 All degrees of cleavage (or symphysis) may occur. In 

 the tricotylous races of Antirrhiniiui ma jus and Serophu- 

 laria nodosa they are particularly abundant, and merge 



Fig. yG. Mercnrialis annua. A, normal seedling; C, cotyl- 

 edons, (i) the first, and (2) the second pair of leaves; 

 B, a tricotylous seedling the first two leaves of which 

 stand opposite one another (1900). 



into the decussate arrangement in the first or second or 

 in some later whorl. In the choice of seed-parents I have 

 always paid attention to this point, although it has onl}- a 

 secondary effect upon the result. Further instances of cleft 

 leaves in the transition from tricotyly to the later normal 

 arrangement were afforded me by Dianthiis barbatiis. 

 Lychnis vespertina, Polygonum Fagopyrum, CoUinsia he- 

 terophylla, Anagallis grandiflora and in large quantities 

 by Fagus sylvatica (Fig. 75) as well as by many other 

 species. As the phenomenon is quite common when 

 more extensive sowings are made and as, especially in 



