272 DROSOPIIYLLUM LUSITANICITM. [Chap. XV. 



changed colour of litmus paper, more strongly acid than that 

 of Drosera. This fact was observed repeatedly; on one oc- 

 casion I chose a young leaf, which was not secreting freely, 

 and had never caught an insect, yet the secretion on all the 

 glands coloured litmus paper of a bright red. From the 

 quickness with which the glands are able to obtain animal 

 matter from such substances as well-washed fibrin and car- 

 tilage, I suspect that a small quantity of the proper fer- 

 ment must be present in the secretion before the glands 

 are excited, so that a little animal matter is quickly dis- 

 solved. 



Owing to the nature of the secretion or to the shape of 

 the glands, the drops are removed from them with singular 

 facility. It is even somewhat diflficult, by the aid of a finely 

 pointed polished needle, slightly damped with water, to place 

 a minute particle of any kind on one of the drops; for on 

 withdrawing the needle, the drop is generally withdrawn; 

 whereas with Drosera there is no such difficulty, though the 

 drops are occasionally withdrawn. From this p)eculiarity, 

 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 crawl- 

 ing of the insect, as from its wings being clogged by the se* 

 cretion it .cannot fly away. 



There is another difference in function between the 

 glands of these two plants : we know that the glands of Dro- 

 sera 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 Drosophyllum, the amount of secretion never ap- 

 peared to be in the least increased. As insects do not com- 

 monly adhere to the tnllcr glands, but withdraw the secre- 

 tion, we can see that there would be little use in their having 



