62 A MONTANE RAIN-FOREST. 



as low as 90 per cent. Lloyd attributes the efficacy of absolute alcohol 

 in the fixation of stomata to its rapid dehydrating power, and found 

 that the presence of a layer of mesophyll cells beneath a piece of epi- 

 dermis which had been treated to absolute alcohol affected the openness 

 of the stomata. I have found the openness to be little affected by 

 underlying pieces of mesophyll thin enough to permit measurement of 

 the stomata above them. It would appear, then, either that grades 

 of alcohol below absolute are sufficiently active in dehydration to fix 

 the walls of the guard cells, or else that the principle involved in this 

 method is not that from which Lloyd started in the development of it. 



My measurements of stomata have been made in microns and the 

 averaged values for each reading are given in the tables. I have com- 

 monly read 24 stomata in each preparation, and have found that two 

 such series agree within 1 to 6 per cent, in spite of the variability of 

 the openness to which I shall draw attention. The stomatal datum 

 used in plotting is the square root of the product of length and width 

 of the averaged readings. This gives a figure which is proportional 

 to the diameter of a circle of the same area, and is used in conformity 

 with Brown and Escombe's law of the static diffusion of gases. 1 



DAILY MARCH OF TRANSPIRATION. 



The daily march of transpiration has been ascertained for eight 

 species: Alchornea lati/olia, Clethra occidentalis, Dodoncea angustifolia, 

 Pilea nigrescens, Peperomia turfosa, Peperomia baseUcefolia, Asplenium 

 alatum, and Diplazium celtidifolium. This group of species is repre- 

 sentative of the trees, shrubs, herbaceous flowering plants, and hygro- 

 philous ferns of the rain-forest. The several days on which the deter- 

 minations of transpiration march were made were somewhat unlike 

 as respects weather conditions, but varied only slightly around the 

 normal type of day that has already been described as characteristic of 

 the region (p. 17). The principal feature of the daily weather condi- 

 tions that impresses itself on the curve of transpiration is the hour at 

 which the clearness of the early morning is terminated by clouds or 

 floating fog from the main ridge of the Blue Mountains. The daily 

 curve of evaporation is influenced by the same variable weather con- 

 ditions, and its shape for a given day bears a rather constant relation 

 to the daily curve of transpiration. 



The maximum transpiration for the day may occur as early as the 

 period from 8 to 9 a. m., as is shown for Clethra and Alchornea in 

 Experiment 1 (table 16, fig. 2), and for Dodoncea in Experiment 2 

 (table 17, fig. 3). More commonly the maximum occurs between 

 10 and 12 a. m., or is sometimes registered as late as 1 p. m. in two-hour 

 readings taken so as to terminate at that hour (see tables 17, 18, 19 

 and 20). On the days which remain permanently or intermittently 

 cloudy after the first obscuring of the sun, the transpiration shows a 



ifirown, H. J. and Escombe, I. Static Diffusion of Liquids and Gases in Relation to the 

 Assimilation of Carbon. Phil. Trans. Roy. Soc. London, 193 : 283-291, 1900. 



