194 BOTANICAL GAZETTE [MARCH 
water required in a humid atmosphere, a number of individual 
plants or clumps of plants with undisturbed substratum were 
brought into the laboratory and the leaves allowed to dry off, but 
not to curl through too great loss of water. The plants were then 
placed under bell jars in which the humidity was kept above go 
per cent, and the roots wetted every day or two without wetting 
the leaves. It was not necessary to take any precautions against 
condensation of moisture on the leaves, for whenever the atmos- 
phere in the bell jars approached saturation there was immediate 
condensation on the cool walls of the jar, lowering the humidity. 
The following data record the result of this test: 
Trichomanes rigidum lost turgor in 5 days; dead in 14 days. 
Trichomanes radicans remained normal for 40 days, with the chloroplasts on 
the lateral walls. 
Hymenophyllum microcarpum remained nearly normal for 40 days, some groups 
of cells having become disorganized. 
Hymenophyllum ciliatum remained normal for 40 days. 
Trichomanes capillaceum remained normal for 40 days. 
Hymenophyllum asplenioides remained normal for 40 days. , 
Hymenophyllum polyanthos remained normal and grew for 40° days. 
Hymenophyllum sericeum remained normal and grew for 40 days. 
The only form in this series incapable of maintaining its turgidity 
(Trichomanes rigidum) has already been stated to be one of the 
most hygrophilous, and those capable of growing under the con- 
ditions of the experiment the least hygrophilous of the Jamaican 
species. The extremely low water loss from surface-dry leaves 1» 
a very moist atmosphere can be met, therefore, by root-absorption 
and conduction in all but the most pronouncedly moisture-loving 
species. There are certainly no other common species which rank 
with Trichomanes rigidum in this respect; even the extremely 
delicate T. capillaceum, also requiring the most moist habitats, 
when kept subsequently under the conditions of this test mal 
tained a normal condition for 35 days, at the end of which time the 
experiment had to be discontinued. 
The conduction of root-absorbed water to the leaves is through 
a vascular system very poorly developed as respects the number and 
size of the water vessels, and the path of the water from the veins 
of the leaf to the transpiring cells lies through other cells, perhaps 
