CONCENTRATION OF TISSUE FLUIDS OF EPIPHYTES 505 



record itjis occurring &quot;on trees, rocks, and dry banks,&quot; gives on the 

 average A = 0.51, p = 6.1 in the Leeward ravines and A = 0.55, 

 P = 6.6 in the ruinate. Prescottia stachyoides from the windward 

 ravines and slopes gave an average depression of A = 0.52, or an 

 average concentration in atmospheres of P = 6.3. 



All of these values are distinctly, and in many cases very much, 

 greater than those obtained from the individual species of epiphytic 

 Orchidaceae. 



For comparison with the epiphytic Peperomia we have only 

 Peperomia stellata, which we collected in Jamaica only as a terrestrial 

 herb. It gave the following values: 



Leeward ravines, A = 0.43, P = 5.2 

 Ilidge Forest, A = 0.45, P = 5.4 

 Leeward habitats, A = 0.42, P = 5.1 



These values are slightly higher than the averages for any of the 

 epiphytic species from the rain forest. 



As far as I am aware, the only determination of osmotic concen 

 tration of the tissue fluids of any bromeliad hitherto made is that for 

 Bromelia Pinguim, which Mr. Lawrence and I (19176) found growing 

 as a terrestrial plant in the Jamaican coastal deserts. This gave 

 A = 0.63, P = 7.6. This is a value higher than any of those recorded 

 in this paper with the exception of those for Dendropogon itsneoides. 

 It is, however, extremely low for such a habitat as the Jamaican 

 Coastal Deserts. 



With regard to two species which Mr. Lawrence and I treated with 

 the terrestrial vegetation but which others have observed growing as 

 air plants, the following points may be noted. 



The woody-stemmed Blakea trinervia, which may be rooted in the 

 soil or, accordmg to Shreye, grown as an epiphyte, has a concentration 

 measured by^ = 0.58, P = 6.9, as compared with the general average 

 of A = 0.81, P = 9.7 for the ligneous species of the windward habitats 

 in which it occurs. 



Tradescantia multiflora, which we included with terrestrial vege 

 tation in our earlier paper, but which may also occur as an epiphyte, 

 gave in a single determination_A = o.^^P = 4.7. This is far lower 

 than the general averages of A = 6.3, p = 7.6 for the herbs of the 

 Leeward ravines. 



