334 



LECTURE XX. 



substances of ripe seeds behave differently, according as the other reserve-material 

 is starch or fat. In starchy seeds (e. g. Beans, Peas, the cereals, Chestnuts, etc.) the 

 cavity of the cell is for the most part filled with starch-grains, the interspaces between 

 these containing proteid substances in the form of small, spheroidal granules, which 

 in the Leguminoseae consist of vitellin, in the cereals of a mixture of various proteid 

 matters, and in the Wheat particularly of gluten. In fatty seeds (as those of the Coni- 

 ferese, Palmese, Cucurbitaceae, Umbellifer^, Solaneae, Euphorbiacese, etc.) matters are 

 quite different. Here, in thin sections through the tissue of the reservoir of reserve- 

 materials (endosperm or cotyledons) the cell-cavities are seen to be filled for the most 

 part with rounded brilliant granules, the so-called aleurone-grains, which always consist 

 of proteid substances. The interspaces between these are chiefly filled with amor- 

 phous fat, after the careful removal of which a scanty net-work, poor in substance 

 and of protoplasmic nature, is found, as shown in Fig. 232. The aleurone-grains 



are soluble either in pure water or in very 

 weak alkaline solutions, or also in a iqo/o 

 solution of common salt. They, in their 

 turn, contain so-called globoids — i. e. sphe- 

 roidal, brilliant, minute bodies, said to con- 

 sist of phosphates of lime and magnesia, 

 and which at any rate probably always 

 contain a magnesium salt \ In some 

 cases, but by no means very frequently, a 

 crystalloid of proteid substance is con- 

 tained in each aleurone-grain : these crys- 

 talloids are particularly fine in Ricijius and 

 other Euphorbiacese, and also in the coty- 

 ledons of the Brazil nut {Bertholeiia ex- 

 celsa), one of the Myrtaceae, and in the en- 

 dosperm of Musa Htllii, and many other 

 seeds. These crystalloids remain behind 

 when the amorphous proteid substance 

 surrounding them has been dissolved by 

 water : they are thus less soluble than the latter. According to Schimper's very 

 careful researches, all the crystalloids of proteinaceous substance hitherto known 

 belong either to the regular system, as the cubes in the Potato and the octahedra 

 in the aleurone-grains of Ricinus, or to the hexagonal system, as the large 

 rhombohedral crystals of the Brazil nut, and those of 31usa Hillii and Spar- 

 ganium ramosum. This is not the place to enter more in detail into the crys- 

 tallography of these remarkable structures : it appears more important for the 

 moment to note that in no case does the whole of the proteid substance of a 



Fig. 233.— Cells from the endosperm of Ricinus cotnmunis 

 (800). A fresh, in undiluted glycerine ; B in diluted glycerine ; 

 C warmed in glycerine ; D after treatment with alcoholic solution 

 of iodine, the aleurone-grains have been destroyed, by sul- 

 phuric acid ; the proteid substance of the matrix remains be- 

 hind as a network. The globoid and (in B and C) the crystalloid 

 are seen in the aleurone-grains. 



der k. bayer. Akademie). On the distribution of crystalloids, see Klein xa. Jahrb. für wiss. Bot. 

 (B. XIII. p. 60). What is said in the text is founded particularly on Schimper's works, ' Über die 

 Kry stalk der eiweissartigen Substajizen' in Zeitschrift für Krystallographie (Leipzig, 18S0), and, 

 further, ' Untersuchtingen über die Prote'inkry static der Pflanzen'' (Stiassburg, 1878). Cp. also 

 Pfeffer m Jahrb. für wiss. Bot., B. VIII (1872). 



1 Cp. Pfeffer's statements in my 'Lehrbuch,' IV. Aufl., p. 55. 



