178 D. P. Penhallow — Tendril Movements in 



accepted. Besides the purely geological and cosmological part 

 of his work, which I do not consider here, and the tables of 

 excentricity, what can be accepted ? The wind theory of the 

 upper oceanic currents, the notion of the great climatological 

 effects of these currents (though by far not in the exaggerated 

 extent given to them by Dr. Oroll), some of his considerations 

 on the conservative effects of snow and ice. The main points 

 on which rests, so to say, the whole fabric in its explanation ofgla- 

 ciation and geological climates generally — the influence of winter in 

 aphelion and perihelion during high excentricity and the calcula- 

 tion of temperatures in proportion to the sun-heat received— are, 

 unfortunately, fallacies. 



Geologists will have to look for other causes to explain the 

 more or less frequent glacial and interglacial periods which 

 their studies lead them to admit. 



Art. XVII. — Tendril Movements in Cucurbita maxima and C 

 Pepo; by D. P. Penhallow. 



(Continued from page 114.) 



Conclusion. 



With these facts before us, we may now proceed to discuss 

 the various phenomena and draw such conclusions from them 

 as appear justified. 



Temperature. — The observations here recorded appear to be 

 in harmony with the views generally received, that within cer- 

 tain limits, and with the conditions otherwise favorable, higher 

 temperatures are promotive of the most rapid growth. Accord- 

 ing to the experiments of Sachs* upon the germinating seeds 

 of Cucurbita, the most rapid growth was found to take place 

 under the influence of a temperature of 33*7° C. ; but we have 

 to observe that the growing embryo was doubtless placed 

 under conditions which permitted the normal tension of the 

 parts upon which observations were made to be fully pre- 

 served. In our own observations, the greatest growth, or 

 greatest tendril movement, was made under a temperature of 

 24"4: C, while the most rapid growth of the vine occurred 

 when the " temperature ranged from 29° to 36*6° 0. It is 

 important, however, not to lose sight of the fact that in these 

 cases, we have to deal with modifying influences which affect 

 growth through the tension of the tissues, a disturbance of 

 which frequently occurs as a result of high temperature. 

 Thus, if we compare an even number of hours of growth when 

 the temperature is above 30° C, with the same number when 



* Text-Book, p. 647, etc. 



