126 REPORTS ON INVKSTIGATIONS AND PROJECTS. 



the branches. There appears to be a constant correlation between the foHar 

 habit of the desert plant and the character of the cortical chlorenchyma. For 

 example, in forms with rudimentary leaves, or with none, as Krameria 

 canescens, Aster sp., Koeherlinia spinosa, the cortical chlorenchyma of the 

 branches is palisaded ; but in leafy plants the chlorenchyma is composed of 

 cuboidal cells. Also in plants in which the leaves are rudimentary, the 

 palisade of the branches is very like that of the rudimentary leaves of the 

 same plant. As regards the distribution of the chlorophyll in the branches 

 it was observed in pith, medullary rays, in wood parenchyma and in paren- 

 chyma of cortex, and it occurs in the secondary cortex of older stems. 

 Chloroph3dl was noted in the pith of stems of so j^reat diameter as 3 cm. 



The persistence of the chlorophyll so deeply in the branches may be asso- 

 ciated with the great intensity of light in the desert which tests on the refrac- 

 tion of light from the plant surface indicate is absorbed by the plants in 

 remarkably high percentages. The recession of the chlorophyll, which occurs 

 nearly pari passu with the increase in diameter of the stem, takes place 

 centrifugally. To this there is the single exception of the lingering of the 

 chlorophyll in wood-parenchyma in the neighborhood of the larger ducts 

 after that in the adjacent medullary rays has disappeared. 



Root-habits, by Dr. IV. A. Cannon. — A survey has been begun which is 

 meant to include the principal types of desert vegetation with a view to 

 bringing to light information concerning the general form and habit of the 

 root-systems of desert plants and determine in what manner the peculiar 

 conditions of absorption, and the requirements of anchorage are met. Seed- 

 hngs as well as mature individuals are examined by means of methods of 

 sluicing which allows the examination of the finest ramifications in situ. 

 One of the interesting discoveries resulting from this work is the fact that 

 such seedlings as those of some opuntias develop storage organs in the roots 

 which function for the accumulation of a reserve water supply until the 

 succulent stems reach a size when they may hold a comparatively large 

 amount. Then the embryonic root storage organs atrophy. 



Soil and Air Temperatures. — The dififerences between the temperature of 

 the soil in which the absorbing organs of a plant are functionating and of 

 the air into which transpiration is taking place form an important element in 

 many of the primary physiological processes, and the results of the earlier 

 studies upon the subject seemed to warrant a continuation of this work. 

 To this end a series of recording apparatus is installed at the Desert Labora- 

 tory, a second at the New York Botanical Garden, while data extending over 

 several months were obtained at Cinchona, Jamaica, during 1905 and 1906. 

 A comparison of the results reveals many dififerences yet to be explained. 



Origin, Distribution, and Physiographic Development of the Flora of the 

 Everglades, by Dr. H. C. Cozvles. — Dr. Cowles had previously made one visit 



