1911] SHREVE—JAMAICAN HYMENOPHYLLACEAE 201 
the weights on successive days while in the chamber. The chamber 
was accidentally opened one night, with a resulting fall in humidity 
that caused a loss of weight in all the leaves in it at the time, as 
indicated in the table by asterisks. 
5th 6th 7th 
day day | day 
Surface- 
: Ist 2d 3d 4th 
dried day day day day 
weight 
Trichomanes rigidum. . . ./r.510 |1.308 |1.293 |1.317 |1.290 |1.260 [1.165 [1.115 
Trichomanes radicans . . .|3.880 |3.500 |3.210 |3.015*|2.787 |2.550 |2.600 |..... 
Hymenophyllum aspleni- 
ee a 0.460 |0.430*/0.450 |0.480 |o.522 [0.530 |o.650 |..... 
ee 0.317 |0.350 |o.402 |0.458 jo.350*/0.462 |..... |..... 
ees oie ue 0.668 jo.755 |0.840 |0.862 j0.914 |0.930 |..-.. |.-..> 
Trichomanes rigidum and T. radicans showed themselves inca- 
pable of even so much as maintaining their original weight and 
became more curled each day, while the other species showed steady 
gains in weight and maintained a perfectly normal appearance. 
The fact that these species behaved differently under the same 
conditions, and that the gain or loss was consistently maintained in 
each case, together with the fact of their behavior being in accord 
with their habitat preferences, gives assurance of the result being 
indicative of their normal behavior. The more hygrophilous species, 
accustomed to being covered with a film of water, fail to maintain 
their turgidity even in the presence of a nearly saturated atmos- 
phere, while the high epiphytes, to one of which at least constant 
wetness is fatal, gain appreciable quantities of water. 
In order to determine whether the hygroscopic activity of the 
leaves of the epiphytic species was merely a physical phenomenon, 
several leaves of H ymenophyllum sericeam were killed in chrom- 
acetic fixing fluid for 24 hours, washed for 24 hours, surface-dried, 
and proceeded with just as the living leaves had been. The fol- 
lowing figures were obtained simultaneously with gains in living 
leaves in the moist box: 
Surf. dry wt.| 1 day | 2 days | 3 days | 4 days | s vost Sad nest 
eRe es oe. 0.621 0.560 | 0.510 | 0.505 | 9-499 0.428 | 0.410 
eS en Pee ee 
