Cuar. XV. SECRETION. 335 
needle, the drop is generally withdrawn ; whereas with 
Drosera there is no such difficulty, though the drops 
are occasionally withdrawn. From this peculiarity, 
when a small insect alights on a leaf of Drosophyllum, 
the drops adhere to its wings, feet, or body, and are 
drawn from the gland; the insect then crawls onward 
and other drops adhere to it; so that at last, bathed 
by the viscid secretion, it sinks down and dies, resting 
on the small sessile glands with which the surface of 
the leaf is thickly covered. In the case of Drosera, 
an insect sticking to one or more of the exterior 
glands is carried by their movement to the centre of 
the leaf; with Drosophyllum, this is effected by the 
crawling of the insect, as from its wings being clogged 
by the secretion it cannot fly away. 
There is another difference in function between the 
glands of these two plants: we know that the glands 
of Drosera secrete more copiously when properly 
excited. But when minute particles of carbonate of 
ammonia, drops of a solution of this salt or of the 
nitrate of ammonia, saliva, small insects, bits of raw 
or roast meat, albumen, fibrin or cartilage, as well as 
inorganic particles, were placed on the glands of Dro- 
sophyllum, the amount of secretion never appeared to 
be in the least increased. As insects do not commonly 
adhere to the taller glands, but withdraw the secretion, 
we can see that there would be little use in their 
having acquired the habit of secreting copiously when 
stimulated ; whereas with Drosera this is of use, and 
the habit has been acquired. Nevertheless, the glands 
of Drosophyllum, without being stimulated, continu- 
ally secrete, so as to replace the loss by evaporation. 
Thus when a plant was placed under a small bell- 
glass with its inner surface and support thoroughly 
wetted, there was no loss by evaporation, and so much 
