432 BOTANICAL GAZETTE [JUNE 
spring with very much segmented leaves. Those started late in 
the year begin to bloom the next spring with nearly entire leaves. 
It is not inconceivable that 7. palustre consists of vigorous secondary 
rosettes of T. vulgare which have rejuvenated in autumn, or for 
some other reason flowered in more juvenile condition than usual. 
If occasional pure stands of such a type are to be found, it may 
even be suspected that ecological conditions there favor fall germi- 
nation and establishment of Taraxacum and fall rejuvenation as a 
consequence. More or less entire-leaved forms, whether regarded 
as distinct species, varieties, or ecological forms of T. vulgare, are 
generally arctic, alpine, or temperate hydrophytic. None of these 
habitats favors very early spring germination or long growing © 
season before blooming the second year. 
Another source of modification comes during good growing 
weather in the case of plants that have completed their flowering 
cycle. Rejuvenation by multicipital branching occurs before 
the last flower scapes are gone, giving a combination of juvenile 
leaves with the scapes which characterize senescence. The 
senescent leaves, present before rejuvenation, very rapidly die and 
decay. This circumstance, that early leaves die as new ones are 
produced, is an important one. The plant thus rapidly loosens the 
bond connecting it with the earlier condition, resulting in an 
isolation of pseudotypes which are really transient phases. 
Field observations have successfully applied WresNER’s finding 
of the effect of moist and dry atmosphere, while experiments have 
verified the truth of it. The effect of a xerophytic habitat is not 
to increase the amount of dissection, but to shorten leaves at all 
stages of senescence. Juvenile leaves become nearly orbicular, 
whereas they may be almost spatulate in a habitat with low 
transpiration. Senescent leaves in a xerophytic habitat are so 
shortened that lobes and incisions become sharply triangular. 
Senescent leaves in a non-xerophytic habitat are much more grace- 
ful and very different in appearance. 
ACHENES.—Aside from the failure of red pigment to develop 
in injured fruits of 7. /aevigatum, achene color seems to be rather a 
fundamental character, varying in degree but not in kind. Homo- 
gentisic acid is a highly specific substance derived from tyrosin, 
and neither was found in non-red fruits, according to HANDEL- 
