376 PHYSIOLOGY 
to divert some of the product into amides by a simple substitution of the 
amide radical, NH 2 , for some H or OH radical. Thus, if the fifth group 
in the glucose chain became HC(NH 2 ), the product would be glucosamin, 
a substance of quite different properties (see p. 360). Like diversion by 
substitution might readily occur if only two or three formaldehyde mole- 
cules had come together. Such processes seem to be the initial steps in 
protein synthesis (p. 380). 
The common main product, glucose, usually accumulates in the cells 
because it is formed faster than it can move away. Finally starch or 
some other stable product appears. The intervening steps are hypo- 
thetical. It seems that at a certain concentration glucose molecules show 
a tendency to combine with each other to form a compound sugar, maltose 
(C^HogOu), which promptly compounds itself in like manner into a 
dextrin and finally into starch. The combinations occur rapidly, and 
the intermediate products are hence obscure. Perhaps the process takes 
place under the influence of third bodies, 
called enzymes; maltase and diastase in 
the cases here cited being the possible 
agents (but see enzymes, p. 399). The 
FIG. 6 49 .-Two chioToplasts starch accumulates in minute granules 
of Rhipsalis, with grains of starch within the chloroplasts (fig. 649), so their 
(*) and minute oU droplets. s troma may be the direct agent in organ- 
After SCHIMPER. . ,1 1 1_ .1. 
izmg the starch, or at least may be the 
seat for the formation of the enzymes which bring this about. These 
grains have a definite structure and a rather uncertain composition (see 
starch, p. 358), for both of which the chloroplast itself may be responsible 
(see leucoplasts, p. 389). 
Removal of products. If a leaf is isolated, the accumulation of the 
synthetic products may reach a point where it interferes with further 
photosynthesis; but in nature this does not occur. Use on the spot, or 
diffusion of such products as remain simple and soluble, or the digestion 
of the more complex and the insoluble ones by enzymes (p. 399) and 
subsequent diffusion, is constantly removing the new materials from the 
leaves and stems to other places where they may accumulate or be used 
(see translocation, p. 393). In darkness or weak light, the transporta- 
tion facilities, temporarily overtaxed in full light, overtake the manu- 
facturing ; the laboratories are cleared, consumers are supplied, and the 
warehouses and distributing centers are filled with the surplus awaiting 
future use. 
