370 PINGUICULA VULGARIS. Chap. XVI. 



these leaves were sent me, each haying canght on an average 2'4 

 insects. To nine of them, leaves (mostly of Erica tetralix) ad- 

 hered ; but they had been specially selected on this latter account. 

 I may add that early in August my son found leaves of this same 

 Erica and the fruits of a Carex on the leaves of a Pinguicula 

 in Switzerland, probably Pinguicula alpina ; some insects, but no 

 great number, also adhered to the leaves of this plant, which 

 had much better developed roots than those of Pinguicula vul- 

 garis. In Cumberland, Mr. Marshall, on September 3, carefully 

 examined for me ten plants bearing eighty leaves ; and on sixty- 

 three of these .(i.e. on 79 per cent.) he found insects, 143 in 

 number ; so that each leaf had on an average 2*27 insects. A 

 few days later he sent me some plants with sixteen seeds or 

 fruits adhering to fourteen leaves. There was a seed on three 

 leaves on the same plant. The sixteen seeds belonged to nine 

 different kinds, which could not be recognised, excepting one 

 of Eanunculus, and several belonging to three or four distinct 

 species of Carex. It appears that fewer insects are caught late 

 in the year than earlier ; thus in Cumberland from twenty to 

 twenty-four insects were observed in the middle of July on 

 several leaves, whereas in the beginning of September the 

 average number was only 2-27. Most of the insects, in all the 

 foregoing cases, were Diptera, but with many minute Hyme- 

 noptera, including some ants, a few small Coleoptera, larvse, 

 spiders, and even small moths. 



We tlius see that numerous insects and other objects 

 are caught by the viscid leaves ; but we have no right 

 to infer from this fact that the habit is beneficial to 

 the plant, any more than in the before given <3ase of 

 the Mirabilis, or of the horse-chestnut. But it will pre- 

 sently be seen that dead insects and other nitrogenous 

 bodies excite the glands to increased secretion ; and 

 that the secretion then becomes acid and has the 

 power of digesting animal substances, such as albumen, 

 fibrin, &c. Moreover, the dissolved nitrogenous matter 

 is absorbed by the glands, as shown by their limpid 

 contents being aggregated into slowly moving gra- 

 nular masses of protoplasm. The same results follow 

 when insects are naturally captured, and as the plant 

 lives in poor soil and has small roots, there can be no 



