152 Transactions of the [Sess. 



in a free or uncombined state. The source from which they derive 

 their supply is the nitrates and salts of ammonia contained in the soil 

 in which they grow, and the medium through which it is conveyed 

 into the substance of the plant is the root. In some plants, however 

 (the so-called Insectivorous or Carnivorous plants), the roots are so 

 feebly developed that they are quite inadequate to fulfil all the 

 functions which they perform in ordinary cases ; and in these plants 

 all or part of the leaves are modified for the purpose of capturing 

 insects and other small animals, from the absorption of which they 

 are able to supplement their otherwise defective nitrogenous supply. 



Carnivorous plants are of two kinds, — viz., 1st, those in which 

 there is a true digestive process ; and, 2d, those in which there is 

 merely decomposition and absorption of the liquid products. To the 

 first group belong Drosera, Diona?a, Pinguicula, K^epenthes, and 

 Cephalotus ; and to the second, Sarracenia, Darlingtonia, and Utri- 

 cularia.^ We shall consider several members of these two groups, 

 taking up in order, in the first, Drosera and Dionsea [Droseracece), 

 Pinguicula (Lentibuliariacece), and Nepenthes {NepentJiacece) ; and 

 in the second, Sarracenia (Sarmcemacea;) and Utricularia {Lenti- 

 buUariacece). 



Drosera. 



This genus is distributed over the temperate parts of nearly the 

 whole Avorld, the plants generally inhabiting marshj^ or boggy ground. 

 In Drosera rotundifolia, the plant consists of a spreading rosette of 

 radical leaves, from the centre of which one or more flower-stalks 

 spring. Each leaf consists of a round leaf -blade supported on a leaf- 

 stalk, and the upper surface of the blade is beset with numerous 

 hair-like structures, with glandular knobs, to which Mr Darwin has 

 applied the term " tentacles." Each tentacle consists of a stalk, at 

 the extremity of which is a glandular knob surrounded by an ex- 

 tremely viscid fluid secretion, which, from its glittering in the sun, 

 has given the plant the poetical name of " Sundew." In the centre 

 of -the leaf-blade the tentacles are short and erect, but towards the 

 margin they get longer and more inclined outwards. A fibro-vascular 

 bundle, consisting of a spiral vessel with some simpler tissues, runs 

 in the interior of the stalk of each tentacle, these elements being 

 continuations of the fibro-vascular system of the leaf. The glands 

 consist of two outer layers of small cells, which are filled with purple 

 granular matter or fluid ; and in the centre are a number of elongated 

 cylindrical spiral cells, which seem to be connected with the spiral 

 vessel of the stalk. 



Fully more than a century ago, the discovery was made by two 



^ There are a few other genera in both groups, but most of them are not as 

 yet in cultivation. These are, in the first group, Drosophyllum, Byblis, and 

 Roridula ; and in the second, Aldrovanda and Heliamphora. 



