W. F. Magie — Surface Tension of Liquids. 189 



From the facts here presented, we feel justified in the follow- 

 ing conclusions: 



1. Growth is promoted by an increase of temperature and 

 humidity. 



2. Growth may be retarded by an increase of temperature 

 when other conditions are not favorable. 



3. The conditions favorable to growth, arising from temper- 

 ature and humidity, may cause greater growth during the day, 

 in opposition to the retarding influence of light. 



4. Growth is retarded by excessive transpiration. 



5. The conditions to which the plant is subjected being va- 

 riable, there is a corresponding periodicity in the vital phe- 

 nomena. 



6. Movements of tendrils and terminal buds, being phenom- 

 ena of growth, are modified by whatever variations of condition 

 afl'ect growth. 



With reference to the circumnutations of the tendrils, the 

 following appear justified : 



1. Movements of the tendril and petiole are due to unequal 

 growth by producing unequal tension of tissues. 



2. The unequal growth is chiefly defined in the vibrogen 

 tissue, which may therefore be regarded as the seat of move- 

 ment. 



3. The band of unequal growth does not arise at successive 

 points of the circumference. 



4. The vibrogen tissue consists of three longitudinal bands, 

 each of which becomes more active in turn, without regular 

 order. 



5. Bending under the influence of irritation results from ces- 

 sation of growth and condensation of structure. 



6. The collenchyma tissue is that which is chiefly concerned 

 in variations of tension under mechanical stimuli. 



7. Coiling results (by contact) from cessation of growth and 

 condensation of structure or (free coiling) from increased ine- 

 quality of tension due to continued growth. 



8. Transmission of impulses is effected through continuity of 

 protoplasm in the active tissues. 



Art. XYIII. — Note on a Method of Measuring the Surface 

 Tension of Liquids ; by W. F. MAG-IE. 



Poisscxn", in his Nouvelle Theorie de 1' Action Oapillaire, p. 

 217, gives a formula determining approximately the height of 

 a large liquid drop standing on a level plate. It contains the 

 capillary constant a, which equals the square root of twice the 



