tgtt] SHREVE—JAMAICAN HYMENOPHYLLACEAE 189 
closely similar, and the difference in the curves of humidity brings 
out strikingly the degree to which the conditions on the forest 
floor differ from the general climatic conditions of the region. 
Epiphytic vegetation in the canopy of the forest is subjected to 
fluctuations in humidity similar to those of the clearing, together 
with the slightly higher range of temperatures. The high and 
constant humidity conditions indicated in fig. 1 are characteristic 
of the deep forests of ravines and lower slopes throughout the Blue 
Mountain region from 1200m. to the highest peaks, while the 
more open forests of the upper slopes and ridges have a climate 
approaching more nearly that of the opening. 
LOCAL DISTRIBUTION OF THE HYMENOPHYLLACEAE.—SCHIMPER* 
has pointed out the distinctness in the character of the epiphytic 
vegetation near the forest floor and in the tops of the highest 
trees as observed by him in the forests of Trinidad and Venezuela. 
There the lowest epiphytes in the forest are tender hygrophilous 
plants which show no structural adaptations to the epiphytic habit 
and are often found as terrestrial plants. On the higher limbs 
and twigs of the largest trees are found xerophilous and succulent 
epiphytes possessing marked specialization in structure and in the 
ecology of reproduction. The Jamaican rain forest region has a 
highly developed erosion topography. Only in the ravines does the 
vegetation approach the stature and luxuriance of such lowland 
forests as were visited by ScHIMPER, and in them may be observed 
the same contrast in the character of the epiphytic vegetation. 
On the slopes, ridges, and peaks the forest trees are not so tall by 
One-half as in the ravines, and the canopy is much more open, par- 
ticularly on the ridges and peaks. This results in the forests 
of the upper slopes being devoid of the epiphytes of the lowest 
levels of the ravine forest, while on the ridges and peaks the epi- 
Phytes which are characteristic of the canopy of the ravine forest 
may be found growing down to the forest floor. In other words, 
the trees of the upper slopes have the same epiphytic flora that 
Would be found in the upper two-thirds of the trees of the ravines, 
While the trees of ridges and peaks have only those that are char- 
d ‘Scumwrer, A. F. W., Die epiphytische Vegetation Amerikas. Bot. Mit. aus 
en Trop. Heft. 1, 1888, 
