1 6 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



reached its general maximum in seventeen days. The accumu- 

 lation of such a balance was accompanied by an actual increase 

 of 5 mm. in length, which would be about .4 per cent, of its initial 

 full length. This upward thrust of the mature joint would of 

 course carry the young bud, the growth of which was measured, 

 and would constitute about .3 per cent, of the upward movement 

 of its apex. 



The most obvious and prevalent feature of the expansion of 

 the old joint was the fact that the greater part of this occurred 

 between 11 A.M. and 2 P.M. daily. Diminished elongation or 

 actual shortening followed soon after 2 P.M. Both the mature 

 and the young joint stood plane in the meridian and during the 

 period of most rapid elongation presented their margins to the 

 source of light. The preparation was accidentally placed where 

 the shadow of a door frame 20 cm. in width and no cm. distant 

 passed across it between 9 and 10 A.M. 



The principal daily variations are illustrated by the tracings 

 March 8-15, and March 15-22. If the records of March 9*, 10 

 and II be considered, it will be seen that the course of variation 

 was such that the length of the old joint remained unchanged 

 through a night with the temperature ranging from 50 down to 

 47° F. A rise in temperature of the air from the last named figure 

 to 63° F. at 4 P.M. was accompanied by the following changes: 

 a slow decrease in length continued from the previous night 

 until 10 A.M., broken by an elongating action while under the 

 passing shadow at 9 A.M. A positive elongation at 55° F. began 

 at II A.M., and was marked in character until i P.M., when it 

 checked, although the temperature was still rising to favorable 

 intensities for absorption, reaching 63° F. at 4 P.M. Before this, 

 however, shortening had begun and continued on through the 

 night with repetition on the following days. This is still more 

 marked in the record of March 15-20. The momentary elonga- 

 tion due to shading was displayed at 9 A.M. Shortening or a 

 very slow increase set in at 2 P.M. and lasted until 11 A.M. 

 Two or three hours of lengthening ensued, then cessation of 

 expansion, complete or nearly so. On March 20th the prepara- 

 tion was set in the open at 8 A.M., the illumination being more 

 intense than in the greenhouse. Elongation began at once and 

 ran five hours, ending suddenly at i P.M. and decrease set in 



