252 DION^A MUSCIPULA. [Chap. XII L 



re-opened. Generally they were so torpid during many 

 succeeding days that no excitement of the filaments caused 

 the least movement. In one instance, however, on the day 

 after a leaf opened which had clasped a fly, it closed with 

 extreme slowness when one of its filaments was touched ; and 

 although no object was left enclosed, it was so torpid that it 

 did not re-open for the second time until 44 hrs. had elapsed. 

 In a second case, a leaf which had expanded after remaining 

 closed for at least nine days over a fly, when greatly irritated, 

 moved one alone of its two lobes, and retained this unusual 

 position for the next two days. A third case offers the 

 strongest exception which I have observed; a leaf, after 

 remaining clasped for an unknown time over a fly, opened, 

 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 un- 

 serviceable." Mrs. Treat, who cultivated many plants in 

 New Jersey, also informs me that several leaves caught suc- 

 cessively 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 Dionaja 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. 233), 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, elongated spaces between the spikes, varying 



