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of 
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1905] BRIEFER ARTICLES 453 
indicates an extremely high degree of adaptiveness to variations in tem- 
perature and water supply. The greatly lessened loss of water from the 
leafless twig of September 14 was certainly in great measure due to its 
comparatively desiccated condition at the beginning of the half-hour 
during which it was allowed to 
transpire. Twigs in vigorous 
leafy condition (May 14) lost 
about 7 per cent. as much water 
through the cortex alone as 
through leaves and cortex taken 
i 
together. 
It is evident that Medicago 
arborea depends for protection 
against the excessive transpira- 
tion mainly upon its summer- 
deciduousness. This is shown 
hot only by the lessened loss of 
Water after defoliation, as above 
Stated, but also by the fact that 
damp soil, as under large trees 
of Quercus Ilex at Lake Fusaro, 
where during the larger part of, 
the day in summer the illumina- 
tion is only from 1 to 5 per cent. 
of the total, the leaves of this 
species are hardly at all decidu- 
ous during the summer. The 
aspect of these shade plants (fig. 
2) is notably different from that 
,, O8€ growing on cliff sides. 
The former are much taller and 
Telatively more slender, with 
Teaves fewer, larger, and longer 
Petioled. Twigs of shade plants 
Save about one and one-half 
times as much leaf area as those 
“qual length from sun plants. 
: N individuals growin 
mn deep shade were less (fit 
0 
4S than on those growing in. 
! 
Fic. 2.—Medicago arborea, shade form, 
wn in a situation with one to five per cent. 
illumination. X?. 
