216 STRUCTURAL BOTANY 



If starch is formed, it has to be rendered soluble, 

 in order to be transportable to the other parts of the 

 plant. It is well known that starch can be converted 

 into sugar by means of a ferment called diastase, which 

 is derived from the protoplasm, and is found, for 

 example, in large quantities in germinating seeds, 

 such as those of Barley during the process of malting. 

 It has been proved that diastase is present in the 

 leaf, and serves to convert into sugar the starch which 

 is formed in the chlorophyll-corpuscles. 



The soluble carbohydrates are transported through 

 the parenchyma, and especially through that part of 

 it which immediately accompanies the vascular bundles. 

 They may either be conducted directly to the seats of 

 growth, such as the apical growing points, or the 

 cambium, to be employed chiefly in the formation of 

 new cell-walls, or they may be conveyed to organs 

 which serve as storehouses of reserve food, such as 

 the endosperm or the cotyledons in a seed, the tuber 

 of a Potato, or the root of a Turnip. In these regions 

 the sugar is very often reconverted into starch by the 

 leucoplastids ; it may, however, be stored up in a 

 soluble form, as inuline in the Dandelion, or cane- 

 sugar in the Beet. In some cases it is employed 

 to form enormously thick cellulose walls, as in the 

 endosperm of many Palms ; these cell-walls are 

 dissolved again on germination, and so rendered 

 available as food for the seedling. In other cases, 

 again, as in oily seeds, the non-nitrogenous food- 

 materials are stored, not as carbohydrates, but as 

 fatty oils. 



