10 FLOWERING PLANTS 
are often very finely divided, thus offering a greater surface 
_ for the absorption of the gases dissolved in water, whilst many 
plants which are only partly submerged have two sets of 
leaves, those floating on the surface not being cut up as those 
under the water are. Submerged water-plants do not trans- 
pire, therefore they have no cuticle and no stomata (p. 77): 
in the case of leaves floating on the surface of the water the 
stomata are on the upper surface. Kerner gives 11,500,000 
of stomata for the leaf of a water-lily of ordinary size. In 
order that the stomata may not get filled with water and 
choked up, the surface of the leaf is such that water runs 
off easily. | 
It may here be mentioned that the tissues of water-plants 
abound in air cavities, which not only help in respiration, but 
give lightness to the plant, enabling it to float (see p. 63). 
Submerged water-plants flower very seldom, and when they 
do are either especially adapted for water-pollination, or their 
flowers may rise above the surface of the water, and in that 
case they may be wind, or insect-pollinated. 
Character  — scrophytes grow in dry situations—as, for in- 
istics of stance, in the steppes of Asiatic Russia and the 
SerOphy lee. pampas of South America, where there is a long 
dry season; in arctic and high mountain regions, in sandy 
and rocky soils, and on seashores. In all these situations it 
is difficult at times for the plant to absorb as much water as it 
requires; the first requisite, therefore, is that the plant should 
protect itself from too great transpiration, and thus adapt 
itself to a lessened supply of water. The leaves of Xero- 
phytes are everywhere characteristic of the group; they often 
have a very thick skin, as in the holly, or they may be 
covered with hairs to such an extent that the green colour of 
the leaf is concealed. Professor Henslow, describing the 
plants of the desert near Cairo, notes the greyness in colour, 
and attributes it to the intense hairiness. Sometimes, instead 
of hairs, a layer of wax is produced. ‘Transpiration may also 
be reduced by a lessening of the number of the stomata, which 
may in addition be sunk in the leaf instead of being on the 
