388 Miscellaneous. 



not form starch in equal quantity with itself, and there certainly 

 appears more starch in the full-grown potato cell than there ever 

 was of protoplasm. Starch is too, I think, denser than protoplasm, 

 which would tend to increase this difference. ISIy own view on the 

 subject is, that the starch granule is truly a cell, having a wall distinct 

 from the contents. I am inclined to believe that the first formation 

 of starch is by a small portion of the protoplasm becoming aggre- 

 gated, as a nucleus, developing over itself a membrane; this membrane 

 then commencing to secrete starch around the original nucleus ; in 

 fact, that they are produced much as the spores of some iVlgse are 

 produced, in which the protoplasm splits into many portions, each 

 secreting itself a cellulose wall. With this addition, I take Schleiden's 

 view of the structure of starch as entirely correct, the only point re- 

 quired being explained by the hypothesis of a membrane, the exact 

 origin of the starch. Indeed, I consider the starch cell as closely 

 analogous to the secreting epithelium cell of animal physiologists — 

 viz. a cell which draws the materials of its growth from the surround- 

 ing fluid, and having reached the limit of its growth, dies as a cell, 

 and becomes amenable to chemical influences. The point on which 

 I lay most stress as proof of its cellular character, is the definite size 

 and shape of the granule. If it be formed, as Schleiden asserts, by 

 mere lavers of deposit, I see no h-priori reason why this process 

 should cease at any particular time, or why the size and shape of the 

 exogenous starch granule should not be as indefinite and unlimited as 

 those of an exogenous tree. A cell, however, has, under the same 

 circumstances, a tolerably definite size and shape. The fully-formed 

 cells of any organ in the same plant agree in the closest manner 

 among themselves as to size and shape, however much they may 

 differ in these respects from the cells of other organs, or from those 

 of the same organ in other plants. This is seen in the clearest manner 

 in undoubted free cells, as spores and pollen grains which in the same 

 plant agree in the closest manner with each other. The cellular 

 character of starch is obscured by the fact that the contents are at all 

 stages solid, so that the use of the compressorium and other means 

 usually employed to determine the cellular character of an object fail 

 from this cause. 



Now, if starch be merely a chemical product of the protoplasm, 

 whence does it obtain the distinct definite form so characteristic of 

 this substance ? The starch granules of each plant have a certain 

 cUstinctive form and appearance peculiar to themselves, by which 

 thev may be recognized under the microscope, and there are few, if 

 any plants, the starch granules of which are precisely similar in form. 

 Crystallization is the only means by which homogeneous substances, 

 whether organic or inorganic, are aggregated into definite forms. No 

 one, however, would call the starch granule a crystal. Starch, also, 

 does not always occur solitary in cells ; it occurs in couipany with 

 chlorophyll, and possibly raphides. If it were formed by exogenous 

 deposition, it seems to me very probable that occasionally one of these 

 foreign bodies might be entangled and enclosed in the sulistance of 



