16 LivinGsTON—EsTABROOK : STOMATAL MOVEMENT IN PLANTS 
iodin in absolute alcohol and the determinations made micro- 
scopically. These consisted in finding the mean number of 
stomata occurring per unit area, on either side of the leaf, and 
measuring with ocular micrometer the length and breadth of the 
stomatal openings. Twenty stomata, taken at random, were 
measured in each case. It was found by repeated tests that the 
average result obtained from twenty stomata was not considerably 
altered by employing a larger number; a higher degree of accuracy 
than that here obtained would entail no great difficulty, but would 
be quite useless in the present state of our knowledge. 
That the stomatal openings in the bits of epidermis fixed in 
alcohol by the method of Lloyd are generally unaltered by this 
treatment, is attested by Lloyd himself, by Miss S. Eckerson* 
and by Renner.t Since the method depends for its efficiency 
upon the rapidity with which the walls of the guard cells are 
dehydrated, it is clear that the reagent used must contain not 
more than a certain amount of water. We are not aware that this 
question of the requisite purity of the alcohol to be used in this 
sort of work has heretofore received attention in a quantitative 
way, and therefore present here the result of an extensive test in 
this regard, using the stomata of Eichhornia as subject. The bits 
of epidermis were placed in a series of “alcohols,” ranging from 
absolute to 80 per cent (volume). We were surprised to discover 
that, for these stomata at least, 90 per cent alcohol was apparently 
as satisfactory for our purpose as was absolute. With over 10 
per cent of water a slight closure of previously open stomata 
could be detected. With more than 20 per cent of water this 
induced closure was marked. In spite of these indications we 
persisted in the use of absolute alcohol for all the tests. 
To bring out the method of handling the dimension data, 
TABLE I is presented. It includes the results of measurements 
of Allium stomata at 3:00 p. m. and at 12:30 a.m. Under each 
hour are first shown the actual dimensions, a and } (the long and 
short dimensions of the more or less elliptical cross sectional area 
* Wekeston, Soph 18) Yh nunmbel mill lesb veaula. dec@Gas a. Ge 
224. 22S 1908. 
t+ Renner, O, Beitrage zur Physik der Transpiration, 
IQIO. 
Bot. Gaz. 46: 221- 
Flora 100: 451-547. 
