Cuar. XIILJ] MANNER OF CAPTURING INSECTS. 251 
and when one of its filaments was touched, closed, though 
rather slowly. Dr. Canby, who observed in the United 
States a large number of plants which, although not in their 
native site, were probably more vigorous than my plants, 
informs me that he has “several times known vigorous 
leaves to devour their prey several times; but ordinarily 
twice, or quite often, once was enough to render them 
unserviceable.” Mrs. Treat, who cultivated many plants in 
New Jersey, also informs me that “several leaves caught 
successively three insects each, but most of them were not 
able to digest the third fly, but died in the attempt. Five 
leaves, however, digested each three flies, and closed over the 
fourth, but died soon after the fourth capture. Many leaves 
did not digest even one large insect.” 1t thus appears that 
the power of digestion is somewhat limited, and it is certain 
that leaves always remain clasped for many days over an 
insect, and do not recover their power of closing again for 
many subsequent days. In this respect Dionea differs from 
Drosera, which catches and digests many insects after shorter 
intervals of time. 
We are now prepared to understand the use of the mar- 
ginal spikes, which form so conspicuous a feature in the 
appearance of the plant (fig. 12, p. 232), and which at first 
seemed to me in my ignorance useless appendages. TI’rom 
the inward curvature of the lobes as they approach each 
other, the tips of the marginal spikes first intercross, and 
ultimately their bases. Until the edges of the lobes come 
into contact, elongated spaces between the spikes, varying 
from the j!, to the ~ of au inch (1:693 to 2°540 mm.) in 
breadth, according to the size of the leaf, are left open. 
Thus an insect, if its body is not thicker than these measure- 
ments, can easily escape between the crossed spikes, when 
disturbed by the closing lobes and increasing darkness; and 
one of my sons actually saw a small insect thus escaping. 
A moderately large insect, on the other hand, if it tries to 
escape between the bars will surely be pushed back again 
into its horrid prison with closing walls, for the spikes 
continue to cross more and more until the edges of the lobes 
come into contact. A very strong insect, however, would be 
able to free itself, and Mrs. Treat saw this effected by a 
rose-chafer (Macrodactylus subspinosus) in the United States. 
Now it would manifestly be a great disadvantage to the 
plant to waste many days in remaining clasped over a 
