Tricotyly and the Arrangement of Leaves. 371 
took place before the cotyledons were dead. In Dipsacus 
syhestris torsus, a race which is usually rich in ternary 
individuals, these are almost without exception decussate 
in early youth. 
On the boundary between the 2- and 3-merous whorls 
2 1 /i>-merous 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 Antirrhinum ma jus and Scrophu- 
larla nodosa they are particularly abundant, and merge 
Fig. 76. Mercurialis 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 only 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 Dianthns barbatus. 
Lychnis vespertlna, Polygonum Fagopynun, Collinsia hc- 
terophylla, Anagallis grandi flora and in large quantities 
by Fag-its 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 
