426 BOTANICAL GAZETTE [JUNE 
been confused at various times with one or the other of the familiar 
species named, and designated accordingly in publications. Beyond 
question some of this confusion has been due to bad taxonomy. 
There is ample reason to believe that more of it has been caused 
by lack of definite boundaries between species. 
Although the two common species mentioned are partheno- 
genetic, sexual species are known and hybrids may exist. Aside 
from this possibility, any explanations offered for the overlap 
between species have been so admittedly hypothetical (10) that 
they need not be rehearsed at this point. It is necessary, however, 
to take inventory of the precise information available with respect 
to variation in Taraxacum and its causes. It is also necessary to 
examine the nature of the criteria used in differentiating species 
and species groups. 
Root.—Generally referred to as perennial, without modification, 
it has long been known to branch multicipitally (4), and to split 
into separate individuals (5). 
Stem.—Usually represented only by a growing point; in the 
absence of light internodes develop (20), giving rise to a vertical 
rhizome (cf. fig. 4). 
Leaves.—Although taxonomists admit great variability and 
the frequency of overlap between leaf characters of different 
species, it is a fact that leaf characters are extensively used in 
species descriptions and often in distinctions. “Habit” as indi- 
cated by leaf orientation is also so used (3), despite a lack of evi- 
dence that the light responses of Taraxacum differ from those of 
other plants. In a saturated atmosphere greatly elongated leaves 
are produced (20). The reverse is true, that dry air shortens the 
longitudinal components of the leaf, although WiEsNER’s statement 
that it slightly increases dissection is open to question. Arctic 
alpine conditions result in a symmetrical dwarfing of the leaves of 
transplants (2). Check and transplant in this experiment were 
of equal age, and show little difference in degree of leaf dissection 
in Bonnter’s original figures. Salt itself is not the direct cause of 
-succulence in leaves of saline soil species of Taraxacum (11). The 
rate of production of leaves in plants of identical age varies with 
the habitat, being less in strong sunlight than in shade (20). 
