DIV. I 



MORPHOLOGY 



185 



network in which falling leaves, etc., are caught and transformed into hunms that 

 retains moisture. Among the Ferns also there are epiphytes which collect humus 

 by means of their leaves. In Asplenium nidus the leaves form a rosette enclosing 

 a funnel-shaped cavity above the summit of the stem, and humus accumulates in 

 this. In species of Polypodium and Platycerium special pocket-leaves and mantle- 

 leaves serve for the accumulation of humus and water. The transformation of 

 the leaves of the Asclepiadaceous plant Dischidia rafflesiana (Fig. 213) goes still 

 further. Some of the leaves form deep pitchers with narrow mouths in which 

 the water of transpiration becomes condensed ; roots which branch freely grow into 

 the pitchers, and obtain not only water but valuable nitrogenous substances. The 

 pitchers are, in fact, usually tenanted by colonies of ants, and their excreta and 

 remains form a source of food to the plant. 



The American Bromeliaceae afford an extreme type of epiphytic plants in which 

 the roots may be completely wanting (e.g. Tillandsia usneoides) or serve for 

 attachment only. The absorption of water is entirely by means of peculiar, expanded, 

 peltate hairs borne on the leaves. In many of these plants water collects in the 

 cavities formed by the closely associated leaf-bases, and the plants are spoken of as 



CISTERN EPIPHYTES. 



(c) Adaptations of Green Cormophytes to special Modes 

 of Nutrition 



The so-called 

 referred to here 



INSECTIVOROUS Or CARNIVOROUS PLANTS must be 



T ). These are plants provided with arrangements 

 for the capture and retention of small animals, 

 especially insects, and for the subsequent solu- 

 tion, digestion, and absorption of the captured 

 animals by means of enzymes. All these 



FIG. 214. Leaves of Drosera rotundifolia. That on the left with its partly incurved tentacles is 

 viewed from above, that on the right with expanded tentacles from the side, (x 4. After 

 DARWIN.) 



insectivorous plants are provided with chlorophyll, and can thus live 

 autotrophically. 



A great variety of contrivances for the capture of insects are made 

 use of by carnivorous plants. The leaves of Drosera are covered with 



