AGRICULTURAL BOTANY. 293 
and the lake-dwellers, consequently, suffered extinction, or were forced to change 
their mode of life. Their distinctive characteristics, at any rate, ceased long 
before the European touched foot upon this continent. Were they exterminated 
by neighboring nomadic tribes, or did they become themselves nomadic in their 
habits ? We may never know, but their total and tragic extinction is most prob- 
able. 
BIOLOGY. 
AGRICULTURAL BOTANY. 
DR. E. L. STURTEVANT. 
Read before Section F, Thursday, August lyth. 
If kitchen garden plants be closely studied in many varieties, it will be found 
that selection has differentiated the various natural species in accordance with 
desired uses. 
It will be noticed that while there is a striking uniformity within varieties in 
those portions of the plant which have not been selected for improvement, there 
is a great variation between these portions which have secured attention on 
account of their uses. Thus, in forty-five varieties of onions growing side by 
side, the foliage is all similar, yet the bulbs vary in size, color, shape and habit 
of formation. The twenty-two varieties of carrots present like foliage, yet unlike 
roots. In sixty kinds of lettuce a likeness of bloom and great unlikeness between 
plants while of edible size. Among sixty-six kinds of tomatoes, a sameness of bloom, 
certain varieties in foliage and growth habit, and a very marked diversity in form 
of fruit borne. It follows from a careful observation of over i, loo named varie- 
ties of kitchen-garden plants, that two series of variations can be distinguished : 
The least marked, the normal variations that occur between the parts not sub- 
jected to conscious selection as being of little account for use; the very marked, 
or artificial variations that are produced by conscious selection exerted upon the 
parts which are valued for their use, and which selection has been exercised 
most stringently upon form. It will be further noticed that according as selection 
for the same purpose has been exercised upon the various parts a parallelism of 
development has taken place between plants of different species, genera and 
orders. This parallelism of development points to a unity of arrangement in the 
forces by which the correspondences are produced. 
The effect of selection concentrated upon visible forms has been to produce 
and fix changes from the natural plant to such an extent as in cases to mask the 
original species so that historical data must supplement morphological data in 
order to connect the genetic record. Thus, for illustration, thereat first seems no 
specific connection between certain cultivated kales, cabbages and cauliflowers^ 
VII— 19 
