62 re:ports on investigations and projects. 



use of strong illuminations and the higher powers of the microscope. The 

 following tentative conclusions were reached : 



(i) Little variation in the actual amount of water in the leaves was ob- 

 served, and the rate of loss was low in the cool air and high humidities of 

 the Carmel region in which the work was performed. 



(2) The beach plants or halophytes showed a lively stomatal activity — a 

 remarkable readiness to wilt and desiccate. In this particular such plants 

 are widely different from the fleshy plants of the desert. 



(3) The osmotic pressures of the thick leaves of beach plants are equiva- 

 lent to 0.2 to 1.3 potassium nitrate, or 7.5 to 48 atmospheres. The pressure 

 in the roots is notably lower, as in other plants. 



(4) The amount of water-vapor which any of these plants may absorb 

 from the air is small and of little significance in the life of the plant. 



Irritability of the Stigma of Diplacns (Moitkcy-flozcer), by Prof. 



P. E. Lloyd. 



The abundance of living material around the laboratory at Carmel led to 

 the testing of the irrito-motile movements of the stigmas of Diplacns, which 

 is one of a group in which the lips of the stigma are capable of pronounced 

 movements on contact. These movements seem to take place only in cells 

 actually pressed or deformed by the contact of a hard object, and no trans- 

 mission of impulse occurs. The application of pollen does not constitute a 

 stimulus and an interpretation of the phenomenon in question as an adaptive 

 function is difficult to make. 



The Water-balance of Succulents, by Dr. D. T. MacDougal. 



Earlier results as to the amount, variation, and physiological value of the 

 great balances of water accumulated by cacti have been brought out in Pub- 

 lication No. 141. A continuation of this work has yielded some further 

 results of importance. The rate of daily loss of water by transpiration 

 from massive cacti was seen to be as high as i in 300 of their total weight in 

 Bchinocactiis (a globose form) and i in about 700 in Carnegiea (a cylindri- 

 cal form). The lowest daily rate was i in 40,000 Bchinocactiis and i in 

 9,000 in Carnegiea. 



Contrary to accepted generalizations, the rate of loss of water is not pro- 

 portional to the degree of succulence or proportion of water present. A fair 

 illustration is offered by an Bchinocactiis which transpired at a rate between 

 10 and 29 grams daily in 1908. A year later, when it had suffered a deple- 

 tion of its water-balance amounting to 7 per cent, the rate fell to 4 to 15 

 grams daily, a decrease of more than 50 per cent. The decrease is not refer- 

 able to heightened concentration of the sap, but must be due in the main to 

 alterations in the character of the membranes and to changes in position of 

 the surface folds, chiefly the first-named cause. 



