lyo PLANT WORLD. 



ends were cut from the petioles, and the leaves were re- 

 weighed for a number of days with the following results: 



While there was some power left in the leaves to absorb 

 water, their failure to take it up continuously, so as to restore 

 the original weight, shows that the 50 days during which 

 they had been isolated was too long a period for them to 

 withstand. The power of entire plants of Sti'Iis to tide over 

 periods of drought was not tested, but is probably not much 

 greater than that of the isolated leaves. 



For the sake of comparison with Slelis two plants of 

 Gnzmauia, still attached by their holding roots to the 

 branches which they had inhabited, were brought under roof 

 at Cinchona and kept for 53 days without wetting. The 

 plants lost a number of the outer leaves of their rosettes, but 

 were still alive at the end of the test, as evidenced by the 

 growth of new leaves when they were again supplied with 

 water. GuzvuDiia, therefore, even in the absence of a stored 

 supply of water is capable of withstanding prolonged drought 

 better than the orchid in which there is a small supply of 

 water that is conserved during drought by a marked cutting 

 down of the transpiration rate. This is in accord with the 

 distribution of Stelis and Giiziiuuiia in the rain forest, where 

 the former occupies mid-heights and the latter, while not 

 absent from mid-heights, is commoner in the highest limbs. 

 The relation between these two types of epiphytes as respects 

 ability to withstand drought and as respects vertical distribu- 

 tion is one which holds, with minor modifications, for all 

 members of the two classes of water storing and non-storino; 

 epiphytes. All of the water storing Orchidace^e and 

 Piperaceae of the Jamaican montane forests are associated 



