1914] HASSELBRING—EFFECT OF SHADING 283 
ence in transpiration the total quantity of dry substance produced 
was the same in both sets of plants. This fact suggests that tran- 
spiration in itself, or the mere passage of water through the plant, 
has no influence on assimilatory activity provided the water supply 
does not fall below a certain minimum required to maintain the 
turgor of the cells.? 
There is another factor, however, to be taken into consideration 
in the discussion of the effect of transpiration on assimilation in 
these experiments. This factor is the reduced illumination to 
which the plants under cheese-cloth were subjected. The work of 
many investigators’? has shown that for many plants in northern 
latitudes light can be considerably reduced without reducing the 
assimilatory activity.® An explanation of this fact is furnished by 
BLACKMAN and Martruaet,” who believe that under natural con- 
ditions leaf temperature and the partial pressure of carbon dioxide 
6 See footnote 12. 
*1 TIMIRIAZEF oe ila cosmical functions of the green plants. Proc. Roy. Soc. 
72:424-461, pls, ; 
Brown, H. T., ap OMBE, F., Researches on some of the physiological pro- 
cesses of green leaves, with ae reference to the oe of energy between the 
leaf and its surroundings. Proc. Roy. = 
BLACKMAN, F. F., Optima and limiti sana tas re Bota tany 19:281-295. 1905 
Lup UBIMENKO, W., ‘Production de la ee fest get et de la chlorophylle chez les 
Végétaux supérieurs a aux différentes intensités lumineuses. Ann. Sci. Nat. Bot. IX. 
7332-415. 1908. 
Comprs, R., Détermination des intensités lumineuses optima pour les végétaux 
aux divers Ses de a Ann. Sci. Nat. Bot. EX. 11:75-249. 1910. 
ergie assimilatrice chez les plants cultivées saus différents eclaire- 
ments, Ann. Sci. Net Bot. IX. 17:1-110. 1913. 
SHANTZ, H. L., The s of artificial shading on plant ha in Louisiana. 
US.D.A. ; Bur. Pl. Industry, Bal 279. 1913. In this paper the data refer to fresh 
a of the plants 
: 
of shading is injurious. SHANDER, ee Uber die physiologische Wirkung der Kup- 
triolkalkbriihe. Landw. Jahrb. 33:517- 584. 901; see also Ewert, R., Der 
: pier 
der _ahze. Landw. Jahrb. 34:233-310. pls. 3. 1905, and Weitere — o Sher = 
ad e und fungicide Wirkung = Kupferbrthen bei ts n Gewiachsen 
der Johannisbeere. Zeitschr. Pflanzenkrank. 22:257-285. 1 
” Blackman, F. F., and MATTE TTHAEI, Miss G. L. CA ea —- of 
* Sting xide assimilation and leaf t temperature in na illumination 
* Soc. B 76:402-460. 1905. 
