FORM IN WHICH RESERVE-MATERIALS ARE STORED, 



333 



the reserve-materials are consumed, are likewise made use of. This is very distinctly 

 the case, for instance, in the scales of the common kitchen onion and the tuber of the 

 potato. In such cases, however, albumin or a soluble proteid substance appears to 

 be present in the cell sap ; in rarer cases a portion, always relatively small, of the 

 non-organised proteid substance may exist in the form of crystalloids. This is best 

 known in the tuber of the common potato, where, especially close beneath the skin but 

 occasionally also in the whole parenchyma, magnificently developed colourless cubes 

 or even tetrahedra are found lying in the protoplasm in autumn and winter. The 



Fig. 229. — A crystalloid of the potato tuber, 

 altered by alcoholic solution of iodine and gly- 

 cerine : in the fresh condition it is a perfect cube. 

 A spherical layer enclosing a small cube has be- 

 come separated in the interior. 



FtG. 230. — A few cells from a very thin section 

 through the cotyledon of Pisu?n satruum. still in the ripe 

 seed. The large grains St with concentric layers are 

 starch-grains (cut through) ; the small granules a are 

 aleurone-grains consisting chiefly of legumin, with a 

 little oily matter ; i intercellular spaces. 



Fig. 231. — Cells from the cotyledon in a ripe seed of 

 Liipinus-varivs. .<^ in alcoholic solution of iodine; Rafter 

 the destruction of the grains fay sulphuric acid, Z cell- 

 wali ; b protoplasmic matrix with little oily matter ; y 

 aleurone grains ; o drops of oil separated from the matrix 

 under the influence of the sulphuric acid ; nt cavities 

 from which the aleurone grains have been dissolved (800). 



careful studies which have been devoted to these crystalloids, and others to be men- 

 tioned later, leave not the slightest doubt, on the one hand, that they consist of proteid 

 substances, and, on the other, that they resemble true crystals in all points, but with 

 the single difference that they are capable of swelling by imbibition ^. The proteid 



*■ The crystalloids were discovered by Theodore Hartig {Bot. Zeit., 1856), and further investi- 

 gated by Radlkofer in his book ^ Uber Krystalle proteinartiger K'orper' (Leipzig, 1859). Bailey 

 discovered the crystalloids in the potato tuber {Flora, 1874, p. 415). Our present views on the 

 nature of ' crystalloids were founded by Naegeli, * Bot. Mittkeilungen,' I, p. 217, 1862 (Sitzungsber. 



