THE FAUNA OF "RESERVOIR-PLANTS." 189 



water and detritus which it collects between its own leaves. It 

 has special absorbent scales on the lower part of its leaves, and 

 these scales take up not only water and inorganic salts but 

 organic substances as well.* Hence the purity of the water ; 

 hence also the fact that the solid debris, deprived of inorganic 

 salts and of organic decomposition-products, consists very largely 

 of cellulose, which substance is present in much larger proportion 

 than it is in the mud of most terrestrial marshes. 



Thirdly, if a vertical section of an epiphytic bromelia be 

 made (see fig. 3), it is seen that the inner part, where the leaves 



Fig. 3. — Diagrammatic vertical section through an epiphytic bromeliad ; 

 explanation in text. (After Picado.) 



are still alive, forms a number of water-holding compartments. 

 So closely do the leaves fit that these interfoliar spaces are 

 isolated from one another, so much so that the water in them 

 stands at different levels. This inner part of the plant has been 

 termed by Picado the " aquarium." The outer part, consisting 

 of the stumps of dead and fallen leaves and of solid debris 

 formerly accumulated in the interfoliar spaces, is termed the 

 ' terrarium " ; in it the compartments are not isolated from one 

 another. 



Now, plainly, all this must have a far-reaching effect on the 



* The fact that bromelias absorb inorganic salts through their specialized 

 scales has long been known, but their power of taking up organic substances 

 has not been so fully understood. Picado's paper is largely concerned with 

 this latter point. As the resiilt of an elaborate series of experiments, he 

 concludes that the plant actively secretes a definite substance which acts 

 chemically on decomposition-products. But it is beyond the scope of this 

 article to enter into this matter in detail. 



