40 
In mj i^aper on the mechanism of stuniiitu, just lUcJ, 1 showoil tliat 
there was diversity even among our few rolypodiacc(v in the eastern 
United States; the range in the Philippines naturally is mneh wider in 
all respects. The turgor of the guard cells has an exeetHlingly wide 
range. In Fteris opaca, it is the same as in the opidernnil colls, or 
(using a familar ellipsis) 0.3 to 0.4 normal i)utassium nitrate. In 
Leptochilus licteropliyUus, it is 0.5 normal potassium nitrate in the guard 
cells, but only 0.4 normal in the epidermis. In Loxogramme iridifolia, 
plasmolysia of the guard cells begins in 0.5 normal solution. In Pro- 
sapiia cryptocarpa and Folypodium dollchopterum, the turgor is 0.7 
normal, that of the epidermis of the latter being the same; and in Nipho- 
holus variiis (other Niphoholus species are not very different) the pore 
closes in a normal solution of potassium nitrate, but plasmolysis is doubt- 
ful even in this concentration. In Niphoholus all neiglihoring cells of 
the stoma plasmolyze before the pore appreciably begins to close. 
Probably a majority of the ferns here and elsewhere in the world are 
similar to Bennstcedtia pundUobula in their stomatal mechanism al- 
though in most of them the development of the ridge of entrance is less 
excessive. Representative of these are NepJirodium sparsum, Leptochilus 
heterophyllus, Fteris opaca and Pohjpodiuju doUchopierum. The stoniata 
of this type are considerably longer than they are broad, and arc struck 
by anticlinal walls only near the ends; usually, in fact, only near one 
end, because of the mode of origin of the stoma. Measurements of the 
stomata of N. sparsum are: 
Open. 
Width of stoma microns.... 3G. 5 
Width of ridge of ontnuice do 3 
Width of guard cell do 16 
Width of pore do 4 
In^KNO. 
N 
35 

17.5 
0' 
The stoma of Pohjpodium doUchoiUerum does not quite close. Ivleasurenients on 
it are: 
Open. 
Width of stoma microns.... 4fi 
Width of pore do 5 
In'^^'KNOa In^KNOg 
45 
0.5 
45 
0.5 
The stoma of Pteris opaca widens 1 fi while the pore opens 3 fi, 
CalUjyteris cordifolia is not very far from this type, opening chiefly by a 
swinging outward of the ridge of entrance; but its width does not change. 
Measurements on it are: 
Open. 
Length 
microns.... 
Width of stoma ^^ 
Width of "pore" ZZZZZ'ZaoZ 
Width of ridge of entrance do 
Some of the stomata close completely. 
Tn^^^KNO, 
81 
82 
35 
35 
12 
5 
6 
0.5 
