202 
PLANT STUDIES 
tance in xerophytic conditions. In 
the cactus plants the peculiar stems 
have become great reservoirs of 
moisture. The globular body may 
be taken to represent the most com- 
plete answer to this general problem, 
as it is the form of body by which 
the least amount of surface may be 
exposed and the greatest amount of 
water storage secured. In the case 
of fleshy leaves and fleshy bodies it 
has long been noticed that they not 
only contain water, but also have a 
great power of re- 
FIG. 181. Twig of com- 
mon locust, showing 
the thorns. After 
KEENER. 
FIG. 180. A fragment of bar- 
berry, showing the thorns. 
After KERNEK. 
taining it. Plant 
collectors have found great difficulty in 
drying these fleshy forms, some of which 
seem to be able to retain their moisture in- 
definitely, even in the driest conditions. 
144. Xerophytic structure. The adap- 
tations given above are generally found 
in plants growing in drouth conditions, 
and they all imply an effort to diminish 
transpiration. It must not be supposed, 
however, that only plants living in 
drouth conditions show these adapta- 
tions. Such adaptations result in what 
is known as the xerophytic structure, 
and such a structure may appear even 
in plants growing in hydrophyte condi- 
tions. For example, the bulrush grows 
in shallow water, and is a prominent 
member of one of the hydrophyte socie- 
ties (see 132) ; and yet it has a remark- 
ably xerophytic structure. This is prob- 
ably due to the fact that although it 
