194 BOTANICAL GAZETTE [MARCH 
any given species at a given time in only a few directions.” Nageli 
also asserts that “the transformation of varieties, species, genera, and 
families, is effected in definite directions, toward greater perfection, 
that is, toward greater complexity. Forms grow as it were toward 
greater perfection. This principle is of a mechanical nature, and con- 
stitutes the law of the persistence of motion in the field of organic 
evolution. Once the motion of evolution is started it cannot cease, 
but must persist in its original direction.” Cope* takes advanced 
ground on this question. He says “variations are not promiscuous or 
multifarious, but are of certain definite kinds, or in certain directions.” 
So much for the philosophers. What are the facts? Every 
botanical variety represents with greater or less accuracy some definite 
line of variation from a specific type. Thus Amérosia trifida L., of 
which the type has large, deeply three-lobed leaves, tends constantly 
to vary toward ovate or oval, undivided leaves, especially in the upper 
parts and in small plants. The most conspicuous of these variants 
constitute the variety iztegrifolia of Torrey and Gray. Aster diffusus 
Ait. is described as “more or less pubescent;”’ but those which are 
much “more pubescent” make up Gray’s variety, Airsuticaulis. The 
common ox eye daisy, Chrysanthemum Leucanthemum, is notably vari- 
able, but the variations are principally in a few quite definite direc- 
tions, the commonest being toward tubular or laciniate rays. 
In horticultural botany we have still better opportunities of observ- 
ing similar facts. A very striking case of variation in definite 
directions was worked out during the fall of 1896 by one of my, 
students, Mr. V. A. Clark, in the case of Coreopsis tinctoria Nutt. This 
western composite has been widely introduced in gardens. French 
and German seedsmen offer many selected named varieties, most of 
which are sold in mixture by American dealers. These varieties, = 
being well represented on our grounds, were suggested to Mr. Sa — 2 
for study and classification. It could hardly have been an accident — 
that the varieties, after careful study and quite without knowledge 
any theory of variation, should have all fallen into one series. 
this species the rays are yellow with a very small but variable maroon 
base. In the varieties this maroon marking constantly encroeyes : 
upon the yellow, until in extreme forms it quite supersedes the bi 
color. One is given the impression that the maroon overlays oe € 
low in this extension ; and this is. encanta indicated by the vel 
‘E. D. i as rome eee nic E —e = ee 
