Vegetable Physiolocjy. 401 



a cell having its wall coated with layers of thickening, and they 

 explained the development as follows : the granules originated 

 as vesicles, which by nutrition expanded and simultaneously 

 formed a second coat inside the first, and so on, all the older 

 expanding at each addition in the interior. This notion was 

 supposed to be borne out by the fact of the inner lamellae being 

 softer and less resisting than the outer ; but this circumstance 

 admits of satisfactory explanation in another way. 



Starch-granules occurring in leaves and other actively-vege- 

 tating organs are almost always small, and scattered through the 

 cell-contents. When the cells of such structures are carefully 

 observed at the periods when the starch is in course of formation, 

 the starch -granules will always be found in connexion with the 

 protoplasmic or albuminous matters, sometimes in the nucleus, 

 very often in the viscid strings of protoplasm running out from 

 this, or imbedded in the layer lining the wall of the cell (fig. 

 16 B). Still more frequently, in green organs, are the starch- 

 granules found in the interior of chloropJiyll granules : to this point 

 we shall return presently. 



Observations made upon seeds, tubers, &c., in which the large, 

 often highly laminated, granules occur, throw a greater light 

 upon the subject : we there see that the connexion with the albu- 

 minous matters is a necessary one — that, in fact, the starch gra- 

 nules are formed through the agency of the protoplasm. It is 

 found that the granules originate, in their earliest form of small 

 round granules, in minute cavities which are produced in the 

 substance of the protoplasm. Step by step in the larger forms 

 the protoplasm deposits the layers wliich constitute the concen- 

 tric coats, until the full size is attained. The excentric position 

 of the minute cavity or point in potato-starch, to2is-les~mois, &c., 

 seems to arise from that end of the granule at which it lies being 

 pushed out, as it were, from the general surface of the layer of 

 protoplasm, thus hanging into the cavity of the cell, invested by 

 a thin coat of protoplasm, by which it is less freely nourished 

 than the other end. The compound granules, like those of oats, 

 &c., are formed by a number of granules originating near toge- 

 tlier in the same mass of protoplasm, and, coming into contact, 

 they become fitted together, and at last the intervening substance 

 vanishes, so that they become firmly coherent. The double and 

 triple granules sometimes found in the potato have the outer 

 coats completely enclosing the whole, the external mass of proto- 

 plasm having deposited this after they had come completely into 

 contact. 



The formation of starch from the protoplasm is well seen in 

 the grain of maize (fig. 14). At an early stage the starch cells 

 ^re densely filled with protoplasm or albuminous matter. The 



