254 WOODY PLANTS OF MASSACHUSETTS. 
little smoke. The best sorts for timber are the white, the Bed- 
ford, the crack-willow, and the goats’ willow, the three first 
of which have been introduced into this country, and are often 
seen growing here. 
The leaves of the willows are devoured by the large black 
caterpillars of the Antiopa butterfly, ( Vanessa Antiopa, Harris's 
Report, p. 219), and the branches are sometimes completely 
stripped. The caterpillar of the fork-tail moth, (Cerura borea- 
lis, ib. 305), is also found on their leaves. A species of plant- 
lice called by Dr. Harris, the plant-louse of willow groves, 
(Aphis Salicti, ib., p. 191), is found clustered together in great 
numbers on the under side of the branches of various kinds of 
willow, and drawing their subsistence from the plant on which 
they live. The grubs of the horn-bug, (Lucanus Capreolus ib. 
p. 40), live in the trunks and roots of old willows, as well as 
in those of apple trees and oaks. 
The male and female trees of the various species of willow, 
are found to differ in their luxuriance and growth, and some- 
what in the quality of the wood. The female is thought to 
srow with more vigor, and to produce larger stems, the male to 
have equal toughness, but to be more slender and delicate. ‘Twhe 
usual properties of our native willows will be mentioned, when 
known, in the description of the several species. 
The willows present greater and more numerous difficulties 
to the student than any other family of plants. ‘These have 
been enumerated by one of the greatest of modern botanists, 
(De Candolle, Flore Francaise, III, 282,) as follows: 1. The 
species are often trees which can be but imperfectly judged of 
from figures or specimens; 2. The male and female are distinct 
plants, so that the knowledge of an individual does not com- 
plete that of the species; 3. The flowers often expand at a dil- 
ferent time from the leaves; 4. The leaves present little varicty 
and few marks of distinction; 5. The seeds are usually unpro- 
ductive, so that we are prevented from rearing doubtful species 
for study ; 6. Most of them grow readily from cuttings, a fre- 
quent and most fertile cause of varieties; 7, and lastly, garden 
cultivation entirely changes their appearance. 
For these reasons and others, there is little certainty in regard 
