116 BOTANICAL GAZETTE 
The effect of an absorptive system extending over the en 
face has already been mentioned in the reduction of the mecha 
and conductive tissues. As such reduction is found mostly in 
merged hydrophytes, it will be seen that 7. usneoides behaves in 
respects much like such plants. 
The scales stand in connection with the water-storage tissue. — 
cells of this tissue lie well distributed among the chlorophyll-b 
cells and keep them in a state of turgescence. Even after a plant 
lost one-fourth of its weight by transpiration, and the leaves | 
become grooved by contraction, the chlorophyll-bearing parend 
is unhurt. It is believed that the leaf shrinkage is due to a 
collapse of the storage tissue upon loss of water, rather than 
decrease in turgescence of the green parenchyma. There is no 
dence that the plant undergoes desiccation and subsequent 
as in the case of Polypodium vulgare.* 
. THE STOMATA. 
In addition to protection afforded by scales, hairs, and 
walled epidermal cells, xerophytes sometimes guard against | 
rapid transpiration by means of the position and structure of 
stomata. Sunken stomata, or those vestibuled by an epidermal 
space, itself with a narrow opening to the exterior, are all well kno 
In some xerophytic plants the usual closing of the pore by the 
cells is assisted in its function of checking transpiration by m 
tions in neighboring parenchymatous or epidermal cells. In 
australis, for instance, there is, according to TSCHIRCH,’ a large 
cellular space adjoining the stoma, partially filled with coiled cell 
' ™Since this paper went to press, one by MEz (g) has appeared on the pl 
of water absorption in certain species of Tillandsia, among them T. 
corrects SCHIMPER’s observations as to the details of the absorptive process, © 
by the stalk cells (Aujnahmezellen) through the usual process of ae 
describes the scale of T. usneoides as having only one stalk cell ins st 
While it is true that two of the cells are very thin, their presence can £ 
out in good sections of mature scales and still more readily in sections wa 
*HABERLANDT, G., Physiologische Pflanzenanatomie. 2d ed. P- 399- 
