Oucurbita maxima and C. JPepo. 113 



and nine were found to occur on a descending temperature, from 

 two to six hours after the maximum for the day had passed. 



Passing to the conditions of humidity, we find that the max- 

 imum movement of tendrils 1, 8b, 8c, and 9, were reached under 

 conditions of great humidity, of all the remainder, when the 

 sky was clear and the sun bright. The rates of movement, in 

 the four tendrils first mentioned, were respectively 2*06, 0*65, 2'6 

 and 2*17 cm , and were obtained when, owing to the humidity of 

 the air, transpiration was not very active. Tendrils 2, 3, 4, 5a, 

 7ab, and 8a, gave respectively 1-7(5, 3-55, 0*85, 144, 0*92, 0-555, 

 and l - 2 Qm , as their maxima of motion. These values were ob- 

 tained while transpiration was excessive, its effect upon the 

 plant being so great, that all the leaves and terminal buds were 

 drooping. Tendrils 5bc, and 6ab, in which the highest maxima 

 were reached, gave respectively 4*55 and 6'50 cm , but these 

 values were reached under conditions of active, though not 

 excessive transpiration, clear sky and bright sun, while the 

 whole plant was in a normally active condition, as shown by 

 the erect leaves and fine healthy color of all parts. The mean 

 rates of movement under the conditions first discussed, show 

 an average of 143 cm , under conditions of favorable humidity, 

 and 0*707 cm , when the air was unfavorably dry, showing that 

 a due amount of moisture in the air is more favorable to growth 

 than its absence, in the ratio of 1 : 0*494. 



Minimum rate of movement. — Of the thirteen minimum move- 

 ments recorded, we find that five occurred between sunset and 

 midnight, two between midnight and sunrise, three between 10 

 a. M. and 1 P. M., and three between 1 P. M. and 4 P. M. We 

 further find that four occurred during a minimum temperature ; 

 four just before the maximum; two just after and three at the 

 very time of maximum temperature. As in our previous divi- 

 sion", taking the figures obtained for Gab, 3, 56c, 8c, and 9 as rep- 

 resenting the true minima for the entire movement of each ten- 

 dril, we find the average temperature at which these movements 

 occurred to have been 22'9 C, while the average temperature 

 for the whole thirteen was found to be 25*8° C. The remaining 

 seven movements of greater rapidity were found under the in- 

 fluence of an average temperature of 28*2° C. The following 

 table will show the relation between temperature and rate of 

 movement as just explained : 



No. of movement. Mean temp. 



Maximum movements 13 26*5° C. 



Minimum " 13 25-8 



Max. movements, (a) rapid 6 27*2 



" " (b) slow 7 24-8 



Min. " (a) slow 6 22'9 



" " (b) rapid.... 7 28'2 



Am. Jour. Sci— Third Series, Vol. XXXI, No. 182, Feb., 1886. 



