Cuar. XV. DROSERACEZL. 305 
power can hardly fail to be beneficial. Nor can the 
benefit be quite so insignificant as it might at first be 
thought, for a moderately fine plant of Primula 
sinensis bears the astonishing number of above two 
millions and a half of glandular hairs,* all of which 
are able to absorb ammonia brought to them by the 
rain. It is moreover probable that the glands of some 
of the above named plants obtain animal matter from 
the insects which are occasionally entangled by the 
viscid secretion. 
ConcLUDING REMARKS ON THE DROSERACEZ. 
The six known genera composing this family have 
now been described in relation to our present subject, 
as far as my means have permitted. They all capture 
insects. This is effected by Drosophyllum, Roridula, 
and Byblis, solely by the viscid fluid secreted from 
their glands; by Drosera, through the same means, 
together with the movements of the tentacles; by 
Dionza and Aldrovanda, through the closing of the 
blades of the leaf. In these two last genera rapid 
* My son Francis counted the 
hairs on a space measured by 
means of a micrometer, and found 
that there were 35,336 on a 
square inch of the upper surface 
of a leaf, and 30,035 on the lower 
surface ; that is, in about the pro- 
portion of 100 on the upper to 85 
on the lower surface. On a square 
inch of both surfaces there were 
65,371 hairs. A moderately fine 
plant bearing twelve leaves (the. 
larger ones being a little more 
than 2 inches in diameter) was 
now selected, and the area of all 
the leaves, together with their 
foot-stalks (the flower-stems not 
peing included), was found by a 
planimeter to be 39:285 square 
inches; so that the area of both 
surfaces was 78°57 square inches, 
Thus the plant (excluding the 
flower-stems) must have borne 
the astonishing number of 
2,568,099 glandular hairs. The 
hairs were counted late in the 
autumn, and by the following 
spring (May) the leaves of some 
other plants of the same lot were 
found to be from one-third to one 
fourth broader and longer wan 
they were before; so that no 
doubt the glandular hairs had 
increased in number, and pro- 
bably now much exceeded three 
millions. 
