146 LECTURE IX. 



the nitrogenous substances stored in the seed from which it 

 was grown. On the other hand, when the plant is supplied 

 with assimilable nitrogen, the increase in weight which the 

 plant exhibits is much greater than can be accounted for by 

 supposing that just so much carbon, hydrogen, etc., is assimi- 

 lated as is necessary to form proteid with the absorbed 

 nitrogen ; there is evidently an accumulation of non-nitro- 

 genous organic substance as well. ^ 



In illustration of these points the results obtained by Boussingault 

 with Helianthus seeds and seedlings may be cited. 



Weight Nitrogen Nitrogen supplied Dry Nitrogen 



of in to the soil weight of of 



seed. seed. as nitrates. plants. plants. 



1. j 0*062 0-0019 0*1536 6*685 0*1126 grammes. 



2. ( O'o68 O"OO2I O'OOOO 0-325 O'OO22 



3. jo*ii6 0-0033 o-oiii ri68 0*0102 



4. I 0*1 16 '0*0033 0*0222 2*120 0*0148 



Plants 3 assimilated 0420 grammes of carbon = 780 c.c. CO 2 , the daily 

 assimilation being 8*75 c.c. CO 2 : plants 4 assimilated 0*848 grammes of 

 carbon = 1566 c.c. CO 2 , the daily assimilation being 17*6 c.c. CO 2 . 



We may here briefly notice the fact that in many cases substances 

 other than starch have been found in chlorophyll-corpuscles. For instance, 

 Briosi failed to detect starch-grains at any time in the chlorophyll-cor- 

 puscles of the Musacese, but found oil-drops instead, and Pringsheim 

 made similar observations on Vaucheria sessilis. It has been found, in 

 the case of the Musaceae at least, that the organic substance first formed 

 is not different from that in other plants. Both Holle and Godlewski, 

 who have carefully investigated the subject, point out that if oil be the 

 substance first formed, its production must take place according to some 

 such equation as the following : 



57 CO 2 -l-52 H 2 O = C 5 7H 104 O 6 + 8o 2 , 



and that this would necessarily involve the evolution of a volume of 

 oxygen considerably larger than that of the carbon dioxide absorbed. 

 As the result of experiment they found that such a relation between the 

 volumes of the gases absorbed and exhaled does not exist, but that the 

 relation is in this case also that which obtains in other plants, namely, 

 that the volume of oxygen exhaled is approximately equal to that of the 

 carbon dioxide absorbed. The substance first formed in the chlorophyll- 

 corpuscles of the Musaceae also is then one which has the ultimate 

 chemical composition of a carbohydrate. 



The oil which was detected in the chlorophyll-corpuscles of the plants 

 above-mentioned is doubtless derived from protoplasm. Its presence is 



