82 A TEXTBOOK OF GENERAL BOTANY 
substances, but many plants have leaves which are especially 
fitted for this function. Such leaves fall rather naturally into 

Fic. 71. Large air spaces in bulbous 
petiole of water hyacinth (Lichhornia 
crassipes). (X 30) 
two general classes: those 
especially fitted for absorbing 
water and the things which 
are ordinarily dissolved in it, 
and those that catch insects 
or other small animals and 
obtain nutrient substances in 
this manner. We may speak 
of these two classes of leaves 
as water-absorbing leaves 
and carnivorous leaves. 
Water-absorbing leaves. 
The leaves of submerged 
plants are not ordinarily ex- 
posed to evaporation and do 
not have cutinized epidermal 
walls. They are surrounded 
by water in which mineral matter is dissolved, and so can absorb 
these substances directly. 
Many plants growing in 
dry situations have leaves 
that are provided with ab- 
sorbing hairs. These may 
be of great advantage to a 
plant by enabling it to ab- 
sorb water from light rains 
which do not wet the soil, 
or even from dew. They 
are of considerable use to 
plants growing in situations 
where for long periods there 
may be dew every night but 








































Fig. 72. Water hyacinth (Eichhornia 
crassipes) with petioles modified as floats. 
(X 3) 
no rain. Dew is condensed on and absorbed by these hairs. 
Some plants have leaves which are especially fitted for collecting 
