Anatomy of Spar tin a Townsendi 7. 
34i 
of meeting their corners project outwards again and meet the walls of the 
lateral cells, forming a cylindrical cavity whose rim in surface view is very 
thick, with the inner side smooth and circular, while the outer is wavy, 
varied, and even pitted (Fig. 3, 1). The hydathodal space is bounded 
therefore partly by four cells, along whose lines of contact are four vertical 
ridges or flanges, with the intermediate portion facing each cell thinner 
walled. 
A transverse section of the leaf shows a flask-shaped organ, as in 
Fig. 3, 2, with the neck projecting into the epidermal cavity described, and 
the swollen basal portion embedded in the underlying tissue ; a radial 
longitudinal section differs inasmuch as the basal part is elongated and 
boat-shaped, as in Fig. 3, y The cap portion of the hydathode has a 
distinctly stratified, mucilaginous 
wall, fitting the cavity tightly yet 
free from its walls. Although in 
the adult plant it is usually on 
a level with the surface or slightly 
below it, in the very young stages 
it projects a little distance beyond. 
It rests on a strongly lignified 
and cutinized collar (Fig. 3, 2, c) 
which marks the region where the 
thin-walled swollen base abuts on 
the retreating sloped lower corners 
of the adjacent epidermal cells. 
This collar is so strongly developed 
as to give the impression of a thick r t , ,, N r 
. . . . Fig. 3. 1. Surface view of hydathode (Jiy), from 
partition at this point. this is abaxial surface of leaf. 2. Transverse section of leaf 
accentuated by a slight projecting showing hydathode : («) nucleus; _ (0 collar. 
/ & r J ° 3. Radial longitudinal section of abaxial surlace ot 
ridge on its inner upper surface, leaf, showing hydathode. 
The basal portion of the hyda- 
thode is elongated parallel to the axis of the plant and has pointed 
pyramidal ends. It is thin-walled and densely filled with protoplasm, in 
the centre of which lies a relatively large nucleus. In addition to shape, 
it is sharply marked off from the surrounding cells by the absence of 
chloroplasts. The protoplasmic content of the cap is also dense, and 
stained sections give the impression of its being connected through the 
narrow neck by numerous strands of protoplasm to that in the lower 
part. A nucleus has also been observed in the cap, placed sometimes 
near the tip, sometimes partly hidden by the collar. The more frequent 
occurrence of nuclei in the cap portion in younger material would 
strengthen the view that the hydathode consists of two cells whose 
common wall has been resorbed at an early stage. 
