Cuar. XILL MANNER OF CAPTURING INSECTS. 311 
who observed in the United States a large number of 
vlants 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.” It 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 Dionza differs from Drosera, which catches 
and digests many insects after shorter intervals of 
time. 
We are now prepared to understand the use of the 
marginal spikes, which form so conspicuous a feature 
in the appearance of the plant (fig. 12, p. 287), and 
which at first seemed to me in my ignorance useless 
appendages. From 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, elon- 
gated spaces between the spikes, varying from the 7; 
to the 1, of an inch (1°693 to 2°54 mm.) in breadth, 
according to the size of the leaf, are left open. Thus 
an insect, if its body is not thicker than these mea- 
surements, can easily escape between the crossed 
spikes, when disturbed by the closing lobes and in 
21 
