OBSERVATIONS UPON THE PHENOM- 

 ENA OF PLANT-LIFE. 



BY PRESIDENT W. S. CLARK, OF THE MASSACHUSETTS AGRICULTURAL 



COLLEGE. 



The observations concerning " The Circulation of Sap in Plants," which I 

 had the honor of presenting before the Board of Agricultnre at their last 

 country meeting, were so kindly received at the time, and awakened so much 

 interest alter their publication, that I have found it impossible to refrain from 

 fnrtber investigations upon the phenomena of plant-life. Among the subjects 

 to which special attention has been directed during the year, the following 

 may be enumerated, viz.: 



First, The structure, composition and arrangement of the winter-buds of 

 hardy trees and shrubs. Specimens for study were collected, in January and 

 February last, from one hundred and forty species, and some facts of interest 

 recorded. 



iSecond, The percentage of water to be found in the branches and roots of 

 trees during their annual period of repose, as well as when in active growth. 



Third, The phenomena and causes of the flov/ of sap from wounds in trees 

 when denuded of their foliage, as well as the flow from the stumps of woody 

 and heibaceous plants when cut near the ground in summer. In connection 

 with this sul>ject, an attempt has been made to determine what species flow,, 

 how rapidly and copiously, and under what circumstances. 



The pressure exerted by the sap exuded from detached roots of trees under 

 ground, as Avell as that exhibited upon gauges placed at different elevations- 

 from the earth, has also been very carefully observed upon a number of species. 



The facts determined are even more remarkable than were noticed last year, 

 and are particularly important in the case of the sugar-maple. 



Fourth, The structure and functions of the bark of exogenous trees, with 

 special reference to the circulation of sap, the formation of wood and the effects 

 of girdling, — concerning all which points many experiments have been under- 

 taken with satisfactory results. 



Fifth, An attempt has been made to measure the expansive force of growing 

 vegetable tissue, and in connection with this experiment numerous other inter- 

 esting observations have been reached. 



These investigations have been instituted by myself; but in carrying them 

 out I have enjoyed the valuable, and in many cases indispensable assistance of 

 gentlemen connected with the agricultural college, either as officers or students. 

 Due credit will be given to each in stating the results of his work. 



