1 66 
XEROPHYTES 
The most simple mode of reducing evaporation is a 
reduction of the transpiring surface, which is very common. 
The leaves of Hakea sp., Grevillea and other Proteaceae, 
Rubus australis , Russelia, &c., are much branched into fine 
segments which expose but little surface for evaporation. 
Comparison with related forms or observation of seedlings 
shows in most of these cases that a real reduction of leaf- 
surface has occurred in the phylogeny. In many Ericaceae 
the leaves are narrow and needle-like, and often more or less 
rolled back, and this ericoid type of leaf is found in many 
xerophytes, eg. Aspalathus, Epacridaceae, Empetraceae, 
many Rutaceae (eg. Diosma), Rhamnaceae, &c. ; a some- 
what similar form occurs in Ulex, and in Pinus and other 
Conifers. The leaves of Cupressus and other Conifers are 
reduced to small green scales closely pressed against the 
stem ; this form occurs in many New Zealand alpine Vero- 
nicas and in other xerophytes. In these cases the stem 
usually does some of the assimilation, and a further progress 
in this direction leads to cases in which all the green tissue 
is found in the stem and the leaves are reduced to scales, 
the stems retaining their more or less cylindrical form, eg. 
in Casuarina, Cytisus sp., Spartium, Baccharis, Restio, 
Juncus, Ephedra, &c. They are usually grooved lengthwise, 
and the green tissue and stomata occupy the bases of the 
grooves. In some species of Baccharis, Genista, and others, 
the green stems have their assimilating surface increased by 
the presence of longitudinal wings ; this leads on to such 
cases as Bossiaea, Carmichaelia, Muehlenbeckia, Phyllan- 
thus, &c., with long shoots transformed into flat green 
expansions ( phylloclades ) which act as leaves, whilst the true 
leaves are reduced to scales. They occur also in Ruscus, 
Semele, &c., as short lateral branches, closely resembling 
leaves (see also Colletia). Standing with their edges to the 
sky they transpire less than a dorsiventral leaf of similar 
size. 
This advantage of phylloclades — the edgewise position — 
is also obtained in many xerophytes which possess green 
leaves. In many tropical Leguminosae, &c., the leaves (or 
leaflets) move upwards or downwards when the radiation 
becomes too intense, and thus expose only their edges or at 
most sloping surfaces to it (p. 49). In Eucalyptus and many 
