yo 
Margaret W. Rea 
margin of the leaf; and marginal groups ceased altogether after the 
eighth leaf from the base. The apical hydathodic organs were large, 
especially towards the top. 
The lowest leaf of the normal shoot had 15 pores and the number 
gradually increased till the seventh, which had a maximum of 40; 
then a fall occurred, at first gradual, but very marked in the case 
of the eleventh leaf where the number was 18, whereas the tenth 
had 33. From the thirteenth leaf to the top or twenty-fourth one, 
only an apical group was present, with a varying number of pores. 
The shade plant showed a strong contrast to the normal one. 
Both the rotund and intermediate leaves had more marginal groups 
of hydathodes and the individual pores were larger. The lowest leaf 
had 44 pores and with a few exceptions these increased in number 
till on the fifteenth 99 were counted. 
In the sun shoot the scars of the first fourteen leaves alone 
remained. From the fifteenth to the eighteenth leaf there was an 
apical group of 8 pores, and in addition the right margins had 1-2 
groups, comprising 3-8 pores. From the nineteenth to the fortieth 
leaf only an apical group of 4-9 pores was present. The reduction 
in the number of pores in the sun plant is very noticeable com¬ 
pared with the number in the normal plant, and this difference is 
much more marked between the sun plant and the shade plant. 
Total number of pores in the several shoots: 
“ Whole” = 381, Normal = 345, Shade = 985, Sun = 153 
The cotyledonary leaves of the outdoor seedling had each an 
apical group of 4 pores, the corresponding leaves of the shade plant 
having each 5 at the apex. 
CONCLUSIONS. 
1. The position on the leaf. 
The hydathodes invariably occur over the marginal termina¬ 
tions of veins, particularly the midrib. It maybe concluded there¬ 
fore that they occupy a definite position on the leaf in relation to 
the conducting system. 
2. The position of the leaf on the shoot. 
Three or occasionally four hydathode groups were developed 
on each margin of the basal leaves; they were fewer in number on 
leaves of intermediate type, and the upper linear leaves possessed 
only the apical group. Epidermal transpiration from the upper 
