INSECTIVOROUS PLANTS. 



395 



inflected depends on the age and vigour of the leaf, and Darwin 

 mentions that they so remain for a much longer time over soluble 

 nitrogenous substances than over those which yield no such 

 matter. When a fly or small piece of meat is placed on certain 

 glands of a leaf, the secretion from the other glands is increased 

 in quantity and becomes acid, and this takes place before they 

 come in contact with the object. At the same time a remark- 

 able movement of the protoplasm takes place, first within the 

 cells of the glands and then within those of the pedicels. This 

 movement Darwin calls " aggregation." When this occurs the 

 cells present a different appearance. Instead of being filled 

 with a homogeneous purple fluid, they now contain variously 

 shaped masses of purple matter suspended in a colourless fluid. 

 The secretion appears to possess, like the gastric juice of the 

 higher animals, some antiseptic power. During warm weather 

 Darwin placed two equal-sized bits of raw meat, one on a leaf 

 and the other on wet moss. After forty-eight hours that on the 

 moss swarmed with infusoria, while that on the leaf was quite 

 free from them. Small cubes of albumen placed in similar cir- 

 cumstances showed that those placed on the moss became threaded 

 with mould, while those on the leaves remained clear, and were 

 changed into a transparent jelly. Although the leaves appear 

 at a glance to be of a reddish colour, they nevertheless contain 

 chlorophyll in their petioles, both surfaces of the blade, and 

 the pedicels of the tentacles, so that they are able to decompose 

 the carbonic acid of the air; but, owing to their feeble root- 

 development, the plants would not be able to obtain a sufficient 

 supply of nitrogen if they had not the power of obtaining that 

 important element from captured insects. 



Regarding the other species of Drosera, of which there are fully 

 a hundred scattered over the globe, it is a matter for regret that so 

 few are as yet in cultivation. Many of the species are highly 

 ornamental and exceedingly beautiful. Besides the British species, 

 there are only about a dozen in cultivation. Of these the most 

 amenable to culture are Drosera dichotoma, D. binata, D. capcn- 

 sis, and D. spathulata. D. dichotoma is a handsome, strong- 

 growing species ; when well grown it has leaves a foot 

 high, each divided into four leaflets. It does not, how- 

 ever, capture insects so freely as some of the smaller-growing 

 kinds ; probably, from its having such strong roots, it may 



