117 
our great staple products are represented in American herbaria 
if at all, by anything better than the merest fragments. 
The illustration of varieties which have been antifcially ae 
duced, _while presenting the greatest difficulties, is by far the 
eresting and instructive. We have to note ei 
distinc classes of these products. We have first those which, 
ke the carrot, parsnip or potato, present no difference of kind 
ne their wild ancestors. They have merely been improved b 
s 
starchiness of the potato, having been exaggerated, while certain 
others, like the bitterness and poisonous nature of the c 
rot and parsnip, have been eliminated. These nee states are 
illustrated einen ancestor and progeny side by side, p 
haps with intermediate forms, and with specimens, coe 
adjusted, of the useful or objectionable constituents extracted 
rom them. any such plants, like our Indian corn, pe 
and apples, present a specific history of long processes of sitiécial 
selection of distinct varieties. A most striking case is that o 
p> 
3 
oo 
ine 
° 
co 
a 
2 
a 
a 
ie] 
_ 
» 
oO 
tad 
2 
a 
i 
p 
5 
[ary 
2 
Q 
= 
rt] 
z= 
a 
2 
a. 
o 
Q 
° 
fi 
murabiy 
culture except for the unalterable element of rainfall, it became a 
desideratum i find a pres of wheat which could flourish in 
f th Department turned its atten- 
tion to similar regions in foreign countries and sent their agent 
to the arid lands of Russia, where many promising varieties were 
found which had evidently resulted, through selection and heredity, 
during a long exposure to such arid pond none: ane iene 
of these varieties would not be com 
of the tissue-changes which had ie cnn the ma sae 
habit. 
Most interesting among such plants is that class which are 
more directly the result of artificial processes. These processes 
consist of the intelligent selection, from wild or cultivated stocks, 
of ancestors for new forms, to possess specific desired characters. 
e stocks so selected must not only present the characters de- 
sired in the progeny; they must show that they are likely to 
