442 Ewart . — The Effects of Tropical Insolation. 
duces a distinct effect upon the power of assimilation which 
may, if the leaf be sensitive and the exposure very severe and 
prolonged, result in a permanent stoppage of assimilation, 
followed by the death of the leaf, wholly or in parts only. 
In all cases, after prolonged exposure, the leaf is paler than 
normal, and may become browned ( Coccnlus Beccari , &c.), or 
in some cases almost colourless (greenish or yellowish white, 
Pisonia , Selaginella). After being examined, the plants are 
kept well shaded, and from time to time fresh portions of the 
still attached leaves are examined, this method being neces- 
sarily adopted on account of the difficulty of obtaining perfect 
recovery in isolated parts. 
Cocculus Beccari. Exposed from 6 a.m. to 4 p.m. Many leaves, 
especially the older ones, more or less yellowish or brownish entirely 
or in patches. Young adult leaves show weak assimilation, chiefly in 
spongy mesophyll, older leaves none or very weak. In one day 
assimilation active in young leaves, in older leaves weak to moderately 
active, in yet others not perceptible, though leaves have not 
become perceptibly greener. After full exposure for three to four 
days, many older leaves are quite yellow, younger leaves green in 
parts and show none or very weak assimilation. Next day weak 
to moderately active assimilation in younger leaves, older yellowish 
leaves none. Of latter many do not recover, although they may 
remain living for several days, the younger leaves finally become 
almost without exception quite green and normal again. 
Pisonia alba , Sparr. Plant exposed for several days. Leaves from 
almost quite white to yellow or yellowish green : latter faint to 
moderately active assimilation. After thirty hours in faint diffused 
daylight, former leaves faintly green and show weak assimilation. 
In three to four days leaves all deep green to yellowish green and 
assimilation active. In the quite white leaves the chlorophyll-grains are 
almost colourless and difficult to distinguish. Such leaves do not become 
towards the close of the dry season of 1896 and during various cloudless days 
during the wet season of 1896-7, the S. W. monsoon of this period being unusually 
well favoured in this respect. A few, chiefly physical and biological, observations, 
were made in Ceylon during the dry period in the spring of 1897 between the 
two monsoons. 
