Curtis: SOME OBSERVATIONS ON TRANSPIRATION 371 
VI. PrERIopICITY OF THE STOMATA 
IV. 
G ASM. 50'S Bt 12 0 Sra S 5 4 5 6 7 
GERANIUM ZONALE, 56 60 zo7 78 67 49 44 64 46 40 
GERANIUM ZONALE, 60 68 128 78 80 62 45 96 55 36 
Temperature, 23 23.5 23 
fygrometer, 47 47 49 
GERANIUM ZONALE, Ig 23:24 08: 46 28 a4 gp: a8: B§ 23 
Temperature, 25 24.5 24 , 
Hygrometer, 36 32 32 
»GARDENIA FLORIDA, 48 75 8 ee PS oe es eS Se 
JUSTICIA ELEGANS, 306 568 460 322 302 270 302 275 255 217 
Temperature, 22.5 22 21.5 
fygrometer, 48 51 53 
FUCHSIA SPECIOSA, 50° 707°" 8g 48 a ee ee 
Temperature, 20 21 20 
flygrometer, 56 54 55 
AvcuBA JAPonica, 43 43 48 44 46 43 42 4¢ 40 40 
Temperature, 19.5 19.5 
Hygrometer, 59 58 
JUSTICIA ELEGANs, 196 175 180 270 176 167 150 154 136 
Temperature, 20.5 20 19.5 
flygrometer, 43 43 44 
morning. At least this might be inferred from the volume trans- 
Pired and the reverse is true in the afternoon. Of interest also is the 
relation of the after effect. The volume for one or more hours 
following the period of illumination in the morning is in excess 
of the volume preceding the period of illumination. In the after- 
noon this relation may not hold good or there may be a slight 
€xcess in the volume following illumination over that of the pre- 
ceding period. While the periodicity would assist in bringing 
about this relation it is evident that under the conditions of ex- 
perimentation it could not produce so constant a rhythm. 
One feature of this work that has been constantly before me 
is the extreme sensitiveness of the plant and the corsequent ne- 
Cessity for the greatest care in avoiding the introduction of disturb- 
‘Ing influences, Burgerstein’s suggestion that transpiration phe- 
Nomena, when possible, should be studied by weighing would 
appear to promise the most trustworthy results. When we con- 
Sider the complex relations existing in the plant and their varied 
Faction to external conditions it would appear that much of the 
_ Work that had been done upon this subject had been prosecuted 
