ALEURONE-GRAINS AND CRYSTALLOIDS. 335' 



seed or other reservoir of reserve-materials pass into the crystalline form, but that 

 amorphous substance is always present in addition ; and that, as it appears, no crys- 

 talloids are met with in the majority of seeds, and certainly not in thp large majority 

 of succulent reservoirs of reserve-materials. Where they occur, they become dissolved 

 during germination, and, like the amorphous reserve-substance as well as that existing 

 as protoplasm, are conveyed into the growing parts, there to serve for the formation 

 of protoplasm. Like starch-grains and other reserve-materials, crystalloids of pro- 

 teinaceous substance occur also in organs which cannot be regarded as reservoirs of 

 reserve-materials in the narrower sense : here they are met with rather as temporary 

 deposits of plastic substance for special purposes of metabolism. Here belong above 

 all the crystalloids discovered by Radlkofer (1858) in the nuclei of cells in almost all 

 the parts of Lathraa Squamaria, as well as those found by Julius Klein in the nuclei 

 of the cells of Pinguicula and Utricularia. Klein found crystalloids, not in the 

 nuclei, but in the living cell-contents of numerous marine Algae, especially the 

 Siphonese (Acetabularia, Bryopsis, Codium, etc.) and many Floridese (Bornetia, 

 Ceramium, Polysiphonia, etc.). Finally, the Rhodospermin crystals discovered by 

 Cramer, which arise from the cell-contents of the Florideae under the influence of 

 salt solution, alcohol, or glycerine, may be referred here. Klein also found crystal- 

 loids in the fructification of Pilobolus, a fungus closely allied to Mucor. 



The various carbo-hydrates are better known chemically than the diflferent 

 kinds of proteid materials. From a physiological point of view, however, it may 

 be shown that even the most different members of this group — starch, the sugars, 

 inulin, and cellulose — are in so far of completely equal value that they can replace 

 one another as reserve-materials. WhUe in most tubers and other succulent 

 reservoirs of reserve-materials, in the cortex and wood of trees, and in many seeds, 

 starch is usually stored up as the reserve-material, we find exactly the same purpose 

 served in the perennial organs of Compositae, in the tubers of Dahlia and Helianthus 

 luberosus, and in the roots of Inula Hellemum, Taraxacum officinale, etc., by a 

 concentrated solution of inulin ; on the formation of new germinal shoots this is 

 made use of in exactly the same manner as starch is elsewhere. In the beet-root, 

 again, cane-sugar is accumulated in the parenchymatous tissues towards the end 

 of the first period of vegetation; and in the bulb-scales of the kitchen onion a 

 mixture of grape-sugar and other kinds of glucose occur, and here play the same 

 part as does the starch in the bulbs of the tulip and crown imperial. But even 

 cellulose itself, which generally occurs only as one of the final products of meta- 

 boHsm, may play the part of a reserve-material. The endosperm of the Date and 

 of some other palms, as well as the large endosperm of the seed of Phytelephas 

 (vegetable ivory), consists of exceedingly thick-walled tissue, the laminated and 

 pitted cell-walls of which are formed of pure cellulose : this is dissolved on germina- 

 tion, and passes over into the seedling in the form of sugar, thus playing exactly 

 the same part as starch, inulin, and sugar do elsewhere. 



A more detailed description of the species of sugars would here lead us too 

 far into the province of chemistry. In plants they always occur dissolved ; and when 

 obtained in the solid form it is either as true crystals, as in the case of cane-sugar, 

 or as crystalline, crumbling aggregates, as in the case of the glucoses. The latter 

 are chemically distinguished particularly by the fact that they easily reduce copper 



