Ewart. — The Effects of Tropical Insolation. 443 
fully green for from seven to ten days. Young but adult leaves exposed 
for ten hours to perpendicular rays are pale green to yellowish green, 
assimilation absent or faint in parts. Next day leaves slightly greener, 
assimilation weak to moderately active. Similar leaves exposed, but 
layer of cold water interposed, show the same colour as before, 
assimilation absent, or in parts weak to moderately active; in some 
leaves weak assimilation in all parts : recovery as before. 
Dendrobium crumenatum , Lindl. Plants exposed to perpendicular 
rays from 6 a.m. to 4 p.m., assimilation weak or absent; leaves 
slightly paler and yield weaker chlorophyll-extract than equal weight 
of shaded leaves. If part of one leaf is covered by paper or tinfoil, 
at end of exposure it is distinctly fresher and greener, and shows 
moderately active assimilation, rest of leaf weak or none. Next day 
nearly all leaves are living, normal ; assimilation is moderate to quite 
active. In a few leaves assimilation is weak or in parts absent, these 
leaves in a few days turn yellow and die. 
Selaginella sp.t Exposed for some days, leaves turn quite pale, 
and become when shaded green again. One day’s exposure causes 
a distinct fading; and many leaves on the exposed side, though green 
to pale green or yellowish green, show weak or no assimilation in parts 
or entirely. If the half of the leaf only is used, the corresponding 
half next morning may show a fairly active power of assimilation. 
Drymoglossum pilosellotdes, Prsl. After ten hours, exposed vegeta- 
tive leaves slightly paler ; chloroplastids normal and with abundance 
of starch ; assimilation weak or absent ; in partially exposed leaves 
with similar abundance of starch, fairly active. Next day assimilation 
moderate to quite active, but in a few leaves none. The latter may 
in some cases remain living for several days without regaining the 
power to assimilate ; they slowly turn pale yellow or brownish yellow, 
and finally die. A weak power of assimilation may return to the 
preparations previously examined if they are kept in a drop of water 
in a damp chamber. 
Adiantum cwieatum , Lug. and Fisch. and A. assimile , Sw. After six 
hours’ exposure, assimilation faint or absent. Leaves paler and some 
may not recover ; the rest in one day show fairly active assimilation. 
A. rhodophyllum. Leaves thicker, stouter, and more resistant. After 
eight hours the leaves are paler than normal, and show weak, or in 
some cases almost imperceptible assimilation ; next day active again. 
If the leaves are old, assimilation may be absent after eight hours’ 
II h 
