47 



deavoured to determine the exact departure from them of the 

 conditions in a number of plant habitats varying in topographic 

 position, exposure and altitude. To this end I secured weekly 

 records with air and soil thermographs and with a hygrograph, 

 and also made observations as to the percentage of cloudiness and 

 fog, and took photometer readings of the intensity of light. The 

 most salient features of the climate are the extreme constancy of 

 the temperature, the height and constancy of the humidity, the 

 prevalence of cloud and fog, and the large amount and frequency 

 of rainfall. 



Selecting certain characteristic trees and herbaceous plants I 

 made a study of their rates of transpiration, using chiefly the 

 method of weighings and the photometer method. The daily 

 march of transpiration was determined by hourly readings, and 

 simultaneous readings were taken of temperature and humidity 

 and of evaporation as registered by a form of evaporimeter devised 

 by Dr. B. R. Livingston. After thus determining the combined 

 influence of natural conditions upon the daily cycle of transpira- 

 tion in certain species, it was my plan to determine the influence 

 in the same species of variations in heat, light and humidity 

 operating separately, but I was able to carry out this plan only in 

 part. The rates of transpiration showed a high degree of sensi- 

 tiveness to changes in temperature and humidity, and under 

 favouring conditions as to these factors and light some high rates 

 were measured. However the extremely low rates which were 

 found to accompany cloudiness and high humidity, together with 

 the prevalence of these conditions, particularly on the northern 

 slopes of the Blue Mountains, point to the annual total of trans- 

 piration being very low as compared with that in tropical lowland 

 vegetation. 



Measurements of the rate of growth of leaves in a number of 

 trees, shrubs and herbaceous plants in the moist mountain forests 

 indicated rates much lower than in tropical lowlands or in the 

 temperate regions, this being true even of the renewing foliage of 

 completely deciduous trees. A series of observations was begun 

 on the periodicity of growth, leafing-out, leaf-fall and blooming, 

 as well as on the duration of life of leaves in forest trees and shrubs 

 but these observations require a longer continuous residence to be 

 made of the fullest value. 



I made observations and did some experimental work with regard 

 to the significance of the wetting of leaves by rainfall and con- 

 densed moisture. Dripping points are but poorly developed in the 

 native vegetation and the occurrence of epiphyceae was found to 

 be independent of the character of the foliage. The wetting of 

 the upper surface of leaves was found to reduce transpiration, but 

 both direct and indirect evidence showed this to be due only in 

 part to the cooling of the leaf. 



Many interesting features were revealed by a study of the ana- 

 tomy of the leaves of certain typical plants. 



A field study of the habitats and local distribution of the filmy 

 ferns was made, and supplemented by an investigation of their 



