40 



THE STARCH CELL. 



starch-yielding plant, since, in reference to fresh vegetables, the quantity of starch 



differs with the season of the year. Thus in the potato the least proportion of 



starch is found at an early and a later period, and consequently the full-developed 



potato is the most valuable. Moreover, the state of health of a plant is of moment ; 



for in disease the secretion of starch diminishes. 



This has been painfully investigated in connexion 



with the potato blight ; and it has been shown 



that not only does the quantity of starch diminish 



with the advent of the disease, but cells of another 



and an injurious nature appear. These new cells 



are of the lowest order of growth, such as the 



mushroom, and received the name of the " potato 



fungus." 



The diagrams, 83, 84, and 85, represent this con- 

 dition ; Fig. 83 showing the potato in a healthy and 

 vigorous condition, with the cellular meshwork 

 filled with starch granules ; Fig. 84 shows the 

 same cells nearly emptied of their contents ; and 

 Fig. 85 the diseased cells occupied by the fungus 

 growth. The inference to be derived from these facts is, that old potatoes are not 

 valuable, and that the diseased parts should be carefully removed. 



Fig. 83. Potato in its healthy and 

 mature condition. 



Fig. 84.- A slice of a potato, as it appears 

 after germination, when it is thoroughly 

 withered ; or as produced by disease, at 

 the commencement of the "potato dis- 

 ease." The cell-wall remains, but nearly 

 the whole of the starch has been removed. 

 A few grains remain, as shown at a. 



Fig. 85. Diseased potato, showing the pre- 

 sence of a fungus at b, and the isolated grain 

 of starch at a. 



The ordinary starch of laundresses is oftentimes prepared from potatoes which are not 

 fit for the food of man ; but the purest kinds are obtained from rice. It is prepared by 

 Bimply breaking up the pulp so as to disengage the starch from the cellular meshes ; 

 then, by maceration, heat, and motion, to rupture the cell- wall of the granule, and 

 to effect the escape of its contents. Lastly, it is filtered, in order to obtain the starch 

 separate from the membranous cell- wall. 



