56 Department of Plant Physiology. 



McCool. In this field new facts have been gained and a report upon 

 this topic has been prepared. This report will be published as soon as 

 confirmatory experiments may be completed with the better facilities now 

 at the disposal of the department through the completion of the new 

 greenhouse. This work will be continued for further reports. 



Nitrogeti-fixation. — Investigation of nitrogen-fixation by fungi, espe- 

 cially by those which are of importance in the conversion of organic 

 matter, has been continued and a special report on this work will be 

 issued during the present autumn. 



Physiological diseases. — In this line of investigation, ]\Ir. Ormond 

 Butler has made a careful study of the important gum diseases of dru- 

 paceous and citrus fruits, as a part of his graduate work. He has deter- 

 mined the factors which are important in the production of these diseases, 

 and has studied carefully the reactions of the plant and the series of 

 changes undergone. A complete report of this work is now ready for 

 publication as a bulletin. The main results will also appear in the Annals 

 of Botany in a few months. 



Environmental factors. — Because of the limitation of funds during the 

 year, it has been necessary to hold in abeyance the experiments and 

 observations previously begun on the effects of certain environmental fac- 

 tors in relation to plant growth. This line of work involves measurements 

 of conditions, and it is necessary to accumulate data throughout a period 

 of years. The shade-tent studies conducted during two seasons are a 

 part of this line of study. Much of the work will also require green- 

 house space, which was unavailable during the period covered by this 

 report. 



Stimulation and toxic studies. — Rather extensive experiments have 

 been undertaken on the relation of plants to toxic agents. Some of the 

 phases of this study are as follows: 



1. The comparative study of the toxic action of various substances in 

 solutions, in special insoluble substrata, and in soils of different types. 



2. Fundamental observations on the method of action of toxic agents. 



3. Effects of toxic agents on the relative development of tops and roots. 



4. The effects on rate of respiration. 



5. The effects on the rate of transpiration. 



6. The effects on the modification of structure. 



7. Field studies of stimulation effects. 



Observations on variation in floral structures. — As a result of graduate 

 work a paper has been prepared by Mr. Dorsey on the variation in 

 the flower of grape. Topics relating to a more careful study of the 

 structure and development of agricultural plants have been assigned as 

 subjects for special investigation by other graduate students. 



