65 



iMom Ihese figures il appears Ihal iti Oxalis, willi tlic lif^lil al V^,, 

 Ihe assimilalion is increased in direct proportion lo Ihe sup|)ly of 

 COg. The limil is reached al ahoul 2.0 mg. per lilrc, i. C niorc Ihan 

 Ihree limes Ihe CO., percenlage (see (ig. 5). For Mrlamlriiun also. 

 under Ihe same condilions, Ihe curve al lirsl lakes a recUhnear 

 course (see lable VIII). Ilere however Ihe limil is aheady reached 

 al Iwice Ihe CO., percenlage (ahoul I.-, mg.; see lahle \'ni). In 

 Stellaria Ihe assimilalion al 7„ is increased much more slowly in 

 respect to the CO2 supply: Ihe limil is reached al six limes the 

 amounl of CO.,. 



At about \ light none of Ihe shade-plants examined shows direcl 

 proporlionalily belween assimilalion and CO^ suj)ply. The increase 

 in assimilation proceeds at a slower rale Ihan Ihe CO., supply 

 would suggest. We may therefore say that Ihe advanlage of a CO., 

 pressure above the normal appears mosl strongly al low inlensilies 

 of lighl. 



Of the sun-plants, Viola iricolor and Saslurtinm palustrc, as is 

 shown by fig. 4, seem to use up the CO., su|)ply entirely al ] 

 light. Brown and Escombe (1902) give for Helianthiis figures which 

 point in the same direction. In two parallel experiments in >stronglv 

 ditTused lighl» (probably ^ — \] the quanlities of CO,, per lilre irec- 

 koned in volume) were respectiveh^ 2.8 and 25. .i3 per 10,000. The 

 ralio belween Ihem is 1 : 6.6. The ralio belween the intensities of 

 assimilation was 1 : 7.2, and therefore about the same. In another 

 case with still slronger light the ralios 1 : 4.i and 1 : 5.3 respeclively 

 were oblained. The only statement made about the light in ex- 

 periments III and IV of the same invesligalors is that il was >in- 

 sufficienl», and the authors do not seem lo have been abie lo come 

 to any certain conclusions regarding the importance of the supply 

 of carbon dioxide at low light-intensilies. 



A priori it can hardly be doubled that exceplions lo the rule of 

 proporlionalily occur in the sun-plants also. I think I have myself 

 found a case of this kind, in Atriplex latifoliiim. The lighl-curve 

 for normal CO2 percenlage shows al. 1 : 2 lighl an assimilation of 

 about 7.0 mg. With a CO., supply of about ii x O..,?, 13.-.' mg were 

 assimilated, with a CO2 supply of about 5x0.57, 16.-.. mg. Ilere 

 therefore, as in the shade-plants al \ lighl, the assimilation is in- 

 creased much more slowly Ihan the (>()., supply. 



ä. — Svensk Botanisk Tidskrift 1!>-JI- 



