— 246 — 



my experiments the percent production at the same time of year 

 was 16.7). 



Lubimenko (1908 p. 321) and Combes (1910 p. 75) have in- 

 vestigated the production of matter in different intensities of light. 

 From Combes' paper I have calculated the percent production 

 of dry matter per day as follows: 



Plant 



Beginning of 

 the experiment 



Termination of 

 the experiment 



Number 

 of days 



Percent 

 produc- 

 tion of 



dry 

 matter 



Date 



Content 

 of dry 

 matter 



Date 



Content 

 of dry 

 matter 



Triticum vulgare. 



Apr. 19 



0.019 



May 24 



0.174 



35 



6.5 o/o 



» » 



» 





July 5 



1.612 



77 



5.9 °/o 



Raphanus sativus 



» 



0.013 



May 8 



0.25 



19 



16.8 0 /o 



Pisum sativum . . 



Apr. 22 



0.127 



May 9 



0.335 



17 



5.9 °/o 



Tropæolum maj us 



June 11 



0.087 



June 22 



0.28 



11 



11.2 o/ 0 



» » 



June 22 



0.28 



July 22 



12.07 



30 



13.4 o/o 





May 24 



0.117 



June 17 



1.178 



24 



10.1 o/o 



According to these investigations the percent production of dry 

 matter may be 10 % to 17 % for quickly growing plants (Helian- 

 thus, Ricinus, Raphanus) 1 ). 



Weber calculates the C0 2 assimilation in Helianthus as 4.1 mg 

 C0 2 per 50 cm 2 per hour, what also corresponds with a percent 

 production of matter of 14.4 %. In my opinion that is a proof 

 that the mean C0 2 assimilation per 50 cm 2 per hour for quickly 

 growing plants is about 4 — 6 mg and that the values found by 

 Sachs and Thoday only hold good for exceptionally favorable 

 conditions, especially very high temperatures, which Sachs also 

 has pointed out. It is desirable that more experiments be car- 

 ried out with Weber's method and that the half leaf method of 

 Sachs also be used in less favorable conditions. 



4. The production of matter in the different phases 

 of development. From the results given in Hornberger's 

 paper we can follow the content and the production of dry matter 

 during the life of a Sinapis plant. The figures are plotted in the 

 curve fig. 6. The seeds were sowed on April 24. During the first 

 six weeks, until about June 6, the shape of the curve is logarith- 

 mic. During this time the new built organic matter is used mainly 

 for the formation of leaves; hence the production of dry matter 



a ) Further investigations on the production of matter in different plants, 

 may be found in Landw. Jhrb. V— IX 1876—80. 



