366 Tricotylous Races. 
Oenotheras differ from the parent species in several char- 
acters ; nevertheless each arises suddenly with its char- 
acters complete. From this fact we conclude that all of 
them must be regarded as the expression of a single in- 
ternal change. A single new elementary character can 
thus affect more or less profoundly a whole group of 
older internal characters. 
We will regard tricotyly, for the present at any rate, 
as the primary expression of a definite internal factor 
which occurs in the latent state in large numbers of di 
cotyledons, though not necessarily in all. It also occurs, 
although as yet in a small group of cases, in the active 
c 
Fig. 73. Scrophularia nodosa. A tricotylous seedling with the 
first whorl of leaves which is ternary also; C, the cotyl- 
edons. From the harvest of 1899. 
state alongside dicotyly. On this point of view the ques- 
tion suggests itself whether this internal factor will per- 
haps also betray itself during the later life of the plant. 
Tricotyly results in an abnormal arrangement of the 
seed-leaves, and thus it is only natural to expect that its 
internal cause may lead to anomalies in the disposition 
of the foliage leaves as well. 
As a matter of fact, this is the case. In the first 
place, in species with decussate leaves, the arrangement 
of the leaves in whorls of three may continue upwards 
from the cotvlerlons (FiV. 73"). Tin's mav be limited to 
