20 SOME RECENT RESEARCHES IN PLANT PHYSIOLOGY 



greater viscosity of the solution richer in sucrose tending to 

 give too low a value for the conductivity. However, even 

 if the conductivity were as high as 800 x 10" 5 mhos, a very 

 high value for a root, the calculation would still show over 

 25 per cent, of sucrose. This result has been arrived at on 

 the assumption that even for such considerable depressions 

 the simple relationship of molecular concentration to 

 depression still holds. This, of course, is not strictly 

 accurate. 



THE CARBOHYDRATES OF THE SNOWDROP. 



In 1911 appeared the final results^of Parkin's work on the 

 carbohydrates of the foliage leaf of the snowdrop (Galanthus 

 nivalis). This plant and some other monocotyledons are 

 peculiar, inasmuch as they store no starch in the leaf, 

 except a negligible amount in the guard cells of the 

 stomata. Accordingly, as starch is not present, it is to 

 be expected from the results of Brown and Morris that 

 maltose will be absent. This surmise was completely 

 borne out, and it was ascertained that in this leaf no carbo- 

 hydrates were present other than glucose, ^-fructose, and 

 sucrose . The problem of the origin of the first carbohydrate 

 of photosynthesis may thus be very directly attacked. 



Preliminary analyses made it clear that the snowdrop 

 leaf is very rich in sugars, which amount to from 20 to 30 

 per cent, of the weight of the dried leaf, or from 4 to 6 per 

 cent, of the fresh leaf. The total carbohydrate content of 

 .the Tropaeolum leaf, including starch, is from 14 to 18 per 

 cent, of the dry weight. Thus there is a large balance in 

 favour of Galanthus. It was also found that in any leaf 

 the amount of sugar increases from above downwards, and 

 at the same time the ratio of sucrose to the hexoses dimin- 

 ishes. This may be seen from Table X. subjoined. 



In leaves picked from plants growing in clumps the 



