26 THE TRUE GRASSES. 



grains. Between these, which often fill nearly the entire 

 space, finely granular albuminous bodies are irregularly 

 distributed or formed into a network of delicate plates, 

 especially distinct in the peripheral layers. The inner 

 cells show them but little, and are still richer in starch- 

 grains. If the albuminoids so fill up the intervals be- 

 tween the starch-grains that the latter seem to be im- 

 bedded in cement, the albumen appears translucent and 

 the fruit is called corneous ; but if the union is less in- 

 timate, there remain numerous small air cavities, and 

 the albumen is opaque and the fruit is mealy. Both 

 conditions may occur in the same species or variety 

 (Wheat), and they seem to be occasioned by differences 

 in climate and soil. Corneous fruits are usually richer 

 in albuminoids than mealy ones of the same species. 



Starch. As to the form of the starch-grains, we must 

 distinguish between simple and compound. The latter 

 (Fig. 8, 6) are large and composed of many angular 

 granules, into which they often separate. Simple 

 grains are generally present with them. The simple 

 grains have central cavities and are either isodiametric 

 and polygonal (Fig. 7, A), or more rarely lens- shaped 

 with rounded edges, in the latter case often distinctly 

 lainellated and without central cavity. These lens- 

 shaped bodies are always mingled with many smaller 

 ones, while the isodiametric grains are of tolerably uni- 

 form size. These characters are constant within most 

 genera, and even within entire tribes ; they are therefore 

 important from a systematic view, although the}" are not 

 without exception. At the time of germination the 

 starch-grains become eaten through by the action of a 

 kind of ferment, so as to be full of holes before they fall 

 apart (Fig. 7. a-g\ The starch-grains of certain kinds 

 of liice (gluten rice), Sorghum (gluten sorghum), and 

 of Millet, Panicum miliaceum, do not turn blue upon the 

 addition of iodine, but red or reddish brown, and swell 

 up very quickly. According to A. Meyer this is caused 

 by their containing amylodextrin and dextrin. The 

 outermost layer and sometimes two or three layers of 

 the albumen (Fig. 8, 5) contain no starch but small oil- 



