Stomata and Hydathodes in Campanula rotundifolia L . 65 
by the curves (see figs. 4 and 5, p. 67). Therefore it is concluded 
that the position of the leaf on the shoot and the habitat may be 
factors in the number of stomata present. Also, considering the 
number of stomata alone, it looks as if there was more transpiration 
from the sun shoot than from either the normal or shade shoots. 
Other factors, however, may serve to lessen the effect of the 
more numerous stomata of the sun shoot. Foremost is the size of 
the stomata and especially of their pores. The large stomata on the 
under surfaces of the lower leaves of the normal and shade plants 
were absent from the under surfaces of the sun shoot. In most 
instances where there was an exceptionally large number of stomata 
per sq. mm. it was noticed that the stomata were small and had 
small pores (ep. 7 , pp. 827 - 828 ). Therefore the transpiration might 
be little more from those leaves with a large number of small 
stomata, than fiom those where the stomata were larger but fewer. 
It may seem peculiar that the sun plant should form so many 
stomata, since considering transpiration alone, it might be inferred 
that the plant would suffer by losing more water than it could well 
spare in such a situation. Possibly, however, the question of photo¬ 
synthesis is of such importance that the plant responds specially 
to it owing to the favourable conditions, and counterbalances the 
stomatal increase by making use of other devices to lessen water- 
loss which will be mentioned later. Haberlandt ( 3 , p. 473 ) suggests 
in this connection that under these circumstances a current of air 
travelling through the whole thickness of the leaf is useful from 
the point of view of gaseous exchange. 
The arrangement of the stomata was the same in all the shoots 
for the upper surfaces of the leaves, therefore neither leaf position 
nor habitat appears to be important. The arrangement was variable 
near the margin for the under surfaces of the leaves, and it is sug¬ 
gested that this is due to leaf position and possibly to other factors. 
It was concluded that the isobilateral tendency of the upper leaves 
of the normal shoot, and especially those of the sun plant, might 
be a factor in the equalization of the stomata on both surfaces of 
these leaves. Further, the linear shape of the upper leaves and also 
their thicker cuticle, as well as the smaller size of the cells in the 
upper leaves, would tend to reduce transpiration. 
Miss Tenopyr( 4 ,p. 216 ) states that “in Campanula rotundifolia 
the broad radical leaves had epidermal cells of an average length 
of *04 mm. and breadth of *039 mm. Those of linear cauline leaves 
had cells -034 x -032 mm., and transitional leaves *038 x -034 mm. 
