hy Green Plants from certain Organic Compounds. 175 



That green plants cannot normally obtain carbon for " assimilation" 

 from any snbstances except carbohydrates or bodies closely related to 

 them ; not from aldehydes or their derivatives, and not from all 

 carbohydrates even. 



That a componnd may be a sonrce of carbon when snpplied to the 

 leaves, but not when snpplied to the roots, and vice versa. 



That (since parasitic and saprophytic plants, and especially fnngi, 

 undoubtedly do always obtain their carbon from complex organic 

 substances) green plants, owing to the normal process of obtaining 

 carbon being from C0 2 , have to a large extent lost the power of using 

 such substances as a source of carbon. 



That many green plants (? all) behave in the same manner 

 towards such substances. 



[Contrast fungi, which often are characterised by decomposing 

 special substances.] 



That (since neither leaves nor roots can avail themselves of carbon 

 in the form of aldehyde or its compounds — formose, allyl alcohol, 

 acrolein, laevulinic acid, &c.) it is still uncertain whether or not a 

 single substance of an aldehydic or ketonic nature is really formed by 

 plants as an intermediate product between C0 2 and H 2 and glucose 

 (or starch) ; but, if such is produced, it can only be polymerised by 

 the plant under special conditions,* probably at the moment of 

 formation. 



* Compare Loew, ' Berickte Deutsch. Cliem. Gesell,,' 1889, p. 470. 



YOL. XL VII. 



P 



