THE TRANSLOCATION OF CARBO- 

 HYDRATES IN PLANTS 



PART I 



By S. MANGHAM, B.A. 



Late Exhibitioner, Emmamiel College, Cambridge ; University Frank Smart Student in Botany 



In the early days of inquiry into the phenomena of plant life 

 one of the problems which investigators attempted to solve was 

 that of the movements of " plant juices." Observation of the 

 growth of crops and of the value of manures had shown that 

 materials were taken in by the plant from the soil and it was 

 obvious that as growth proceeded these materials must move 

 about. But the nature of this movement was not easy to 

 understand. 



It was known that the veins of animals contained moving 

 blood and this served to suggest that the juices of plants also 

 travelled in tubes, a view taken by Cesalpino, who wrote in 1583. 

 He called attention to the existence in the roots of certain fine 

 threads which pass through the stem and spread into the leaves, 

 where they branch repeatedly. These he thought to be the food 

 passages of the plant. The actual motion of the juices " to the 

 place where the principle of internal heat is placed " was com- 

 pared by him to that of the oil traversing the wick of a lighted 

 lamp. 



Little progress was made towards a clearer conception of the 

 movements of the absorbed nutriment until the beginning of the 

 seventeenth century, when Harvey's discovery of the circulation 

 of blood led to the suggestion that there might be an analogous 

 circulation of the fluids inside plants. As the more minute struc- 

 ture of plant stems became known, this circulation theory took 

 an improved form. This was expressed about 1670 by Malpighi, 

 who held the opinion that a crude sap ascended from the roots 

 through the fibrous portion of the wood to the leaves. There it 

 became elaborated into a formative sap, which spread through 

 the rind, and probably the bast bundles, to places of growth or 



256 



