I 



42 



sac formed all around the hair, in all respects similar to tliose 

 formed by natural growth, with the one exception that these arti- 

 ficial sacs did not elongate much, but, on the contrary, usually 

 had their upper ends adhering to the corresponding extremity of 

 the hair. Osmic acid, nigrosin and methylene blue stained the 

 contents of these sacs much more intensely than those of the 

 natural ones, and the hairs themselves presented the same appear- 

 ance, as to color, as their sacs. 



In various parts of the plant there are very many cells filled 

 with red-colored cell-sap. They occur either singly, or in verti- 

 cal rows in the stem and petiole, or in horizontal layers in the leaf, 

 giving the surface its red appearance. The hair-bearing cells 

 of the epidermis also frequently contain red sap. While the sur- 

 rounding parenchyma cells usually contain a great deal of large- 

 grained starch, there is little of it, more frequently none at all, 

 in these cells. Its place is taken up, in the cells of the youngest 

 parts, by mucilage similar to that in the hairs. Besides, there is 

 always the most lively circulation of the plasma to be seen in 

 them. Reagents act on the mucilage in these cells in exactly 

 the same manner as on that in the hairs. Sections from a very 

 young leaf were treated with acetic acid. Along the upper epi- 

 dermis, the cells of which contained mucilage drops, bubble-like 

 excrescences make their appearance just as on the young hairs 

 treated w^ith the same reagent. Methylene blue causes the red 

 coloring matter to gather in one large globular drop in the mid- 

 dle of the cell and stains it blue, while the plasma is still Hving. 



Plasmolysis can be started and interrupted repeatedly, just as in 

 the hairs. 



The true nature and chemical composition of the mucilaginous 

 secretion and the contents of the hairs still remain to be investi- 

 gated more closely. It seems to me, however, that the reactions 

 described positively demonstrate the presence of large quantities 

 of tannin in the mucilage of the hairs. Furthermore, the nigrosin 

 and corallin tests * as well as the optical inspection entitle us to call 

 the bulk)', whitish masses in the hair ''mucilage." Finally, the 

 behavior of these masses on the application of chloriodide of 

 zinc, of sugar and of sulphuric acid, permit us to infer that nitro- 



* Cf. Strasburger, Bot. Pract. pp. io6, 129, etc. 



