THE MOLECULAR FORCES IN PLANTS. 



121 



be examined in water, the disturbing action of which only takes 

 place slowly. If, from the edge of the cover glass, we run in 

 alcoholic solution of Iodine, the aleurone grains stain yellow : 

 they give, in fact, proteid reactions. If sections lying in water 

 are treated with alcohol from the edge of the cover-glass, the 

 crystalloids in the aleurone grains become fairly distinct. On 

 examination of sections in a drop of anhydrous Acetic acid (glacial 

 Acetic acid) the protein grains swell up considerably, the crystal- 

 loids swell and disappear, but the globoids stand out sharply. 



Sections of the endosperm of seeds of Bertholletia excelsa 

 (Brazil nut) are par- 

 ticularly interesting. 

 If absolute alcohol be 

 added to a section 

 lying in water, the 

 characteristic enclo- 

 sures of the aleurone 

 grains come clearly 

 into view (for illustra- 

 tions see PfefPer in 



Pringsheim's Jcllirb. f. single aleurone grains in olive oil. g, the globoid ; fc, the 



wissenschl. Botanik, Bd. 

 8, Tafel 36, Figs. 16 

 and 17). We have 

 here firstly the proteid 

 crystalloids, which in 

 Bertholletia are com- 

 paratively large, and 

 then the globoids, com- 

 pounds of a double 

 phosphate of Calcium 

 and Magnesium. If 

 we treat sections of 

 Brazil nut with 1 per 

 cent, solution of Osmic 



acid (aqueous Solution Fio. 41. Cells from the cotyledons of the pea, m, cell 



nf flio niA ,,,1 "U wall; '' intercellular space; am, starch grains; ol, 



HO, \V fticn neurone grains ; p, ground substance ; n, cell nucleus, 



must be kept in the draw n in after treating the preparation with methyl 



dark), we Shall Observe green Acetic acid " ^agn. 240. (After Strasburger.) 



the crystalloids still more distinctly, since they only slowly become 

 yelloNv, while the rest of the cell contents, and especially the 



FIG. 40. From the endosperm of Ricinus communis. 

 A, an endosperm cell with its contents in water ; B, 



crystalloid. Magn. 540. (After Strasburger.) 



