38 A MONTANE RAIN-FOEEST. 



Tillandsia incurva and Caraguata sintenesii, the epiphytic plants at the 

 high peaks are exclusively small orchids and ferns, polster-forming 

 mosses, xerophilous hepatics, lichens, and Cyanophyceae. 



The summit of John Crow Peak reaches nearly the altitude of Sir 

 John Peak, but is strikingly different from it in its vegetation, owing 

 to its summit being part of a hmestone dyke running southeast into 

 the valley of the Clyde River. The bare rock of the sunamit is eroded 

 into a honeycombed surface with knife-like edges and pockets of soil, 

 in which is supported a stunted and open forest. Cyrilla racemiflora, 

 Rhamnus sphcerospermus, and Eugenia fragrans are here quite common, 

 to the exclusion of the familiar species of the other peaks. Fagara 

 hartii, Brunfelsia harrisii, Eugenia marchiana, Acalypha virgata, Gym- 

 nanthes elliptica, Chcenocephalus sp., and Eupatorium critoniforme are 

 all either peculiar to this peak or characteristic in its vegetation. 

 Drought-resistant shrubs with prodigious thickets of Chusquea domi- 

 nate the upper slopes of John Crow Peak to the almost total exclusion 

 of all the forms characterizing the rain-forest by which it is surrounded. 



EPIPHYTES. 



The epiphytic plants occupy quite as conspicuous a place in the 

 total assemblage of vegetation in the Montane Rain-forests as they do 

 in any of the lowland plant formations of Jamaica. At the lower 

 altitudes to windward of the Blue Mountains the lofty forest is rela- 

 tively poor in epiphytes excepting in the tops of the trees, where Brome- 

 liaceae and Orchidacese are the commonest forms. In the savannas of 

 the southern coast and in the central part of the island the species of 

 Tillandsia are by far the most prominent epiphytes, with which are 

 usually found a number of Orchidaceae and the single species of Bro- 

 melia present in the island. In the rain-forest of the mountains every 

 type of epiphytic plant is represented, the bromeliads, the orchids, a 

 number of woody forms, ferns of every description from the most 

 delicate Hymenophyllacese to extremely small drought-resistant poly- 

 podiums, flowering plants, both hygrophilous and succulent, as well as 

 mosses, hepatics, and lichens. 



Schimper^ pointed out the differences between the epiphytic vege- 

 tation of the forest floor and the canopy, and I have shown in a previous 

 paper'' that a similar difference exists in the case of the Hymenophyl- 

 lacese and that it is determined by the vertical difference between the 

 climate of the floor of the forest and its canopy, a factor which is 

 operative in the case of all the epiphytic vegetation. The contrast 

 between the epiphytes of the lowest level of the forest and the tree- 

 tops is greater than in the lowland forests, due, of course, to the 



'Schimper, A. F. W. Die Epiphytische Vegetation Amerikas. Bot. Mitth. aus den Trop., 

 Heft 1, 1888. 



^Shreve, F. Studies on Jamaican Hymenophyllaceae. Bot. Gaz. 51 : 184-209. Mar., 1911. 



