444 BOTANICAL GAZETTE [JUNE 
drawn that unfavorable conditions per se tend to produce entire 
leaves. 
WIESNER’S figures of the effect of increased moisture, while in 
general borne out by the writer’s observations, must be accepted 
with reserve upon one detail. It is by no means certain that the 
slight degree of dissection visible in the smaller dry-air leaves can 
be attributed to environmental factors (fig. 9). As previously 
noted, WIESNER merely indicates that both sets of leaves were 
from the same parent plant. It frequently happens that multicipi- 
tal branches of various ages occur upon the same taproot (fig. 4). 
Experiments show that the moist-air leaf which he figures is the 
typical form obtained by placing a juvenile rosette with undis- 
sected leaves beneath a belljar. Furthermore, the driest condi- 
tions under which Taraxacum will grow do not prevent the normal 
sequence of entire leaves followed by more dissected ones, although 
it is quite conceivable that they may affect the rate of senescence. 
In the last place, if a mature rosette be placed in saturated air, 
dissected leaves are produced until rejuvenation occurs. The dis- 
tortion figures show, bearing these reservations in mind, that 
saturated air causes production of leaves that are larger and con- 
siderably longer than those grown in drier air. 
Microchemical tests upon plants of various ages and degrees of 
leaf dissection have revealed a number of points of physiological 
interest, of which only one will be mentioned here. In all plants 
tested, from whatever habitat, juvenile leaf form was accompanied 
by high nitrate tests and little reserve carbohydrate. This is not 
unique; unpublished studies of EckERSON, working with Kraus at 
Wisconsin, show that leaf dissection of tomato is increased by 
scarcity of nitrate as compared with carbohydrate. It is moreover 
of interest to recall Lone’s (13) finding, that inner leaves of Taraxa- 
cum rosettes are richer in photosynthate than outer. 
In conclusion, it is to be noted that a rather extensive survey of 
published species descriptions reveals that a considerable number of 
them will fit variants of either T. vulgare or T. laevigatum caused 
by the interplay of the factors that have been described. While 
this statement is presented upon the writer’s responsibility, without 
detailed data, it may readily be verified in one case by an inspection 
