l6o BOTANICAL MICROTECHNIQUE. 



solution of glucose and peptone by the deposit of a sub- 

 stance whose composition is not yet known. 



This " thickening " of the gelatinous sheaths occurs, how- 

 ever, only when soluble albuminoids and a sugar are simul- 

 taneously present in the surrounding fluid, and, like the 

 expulsion described, is independent of the life of the proto- 

 plasm. 



282. According to the investigations of Hauptfleisch (I), 

 the gelatinous formations of the Desmidiacece consist, on the 

 other hand, of single prisms or caps, each of which covers a 

 pore in the cell-wall. These pores are occupied by threads 

 of protoplasm which commonly terminate externally in 

 globular swellings which penetrate to a greater or less dis- 

 tance into the gelatinous covering, in different species (cf. 

 Fig. 33, /Fand F). 



For the observation of these structural relations, this 

 author recommends that at first dilute, and then gradually 

 more concentrated solutions of safranin, fuchsin, gentian 

 violet, methylene blue, or methyl violet, be allowed to run 

 from the edge to the living algae under a cover-glass, and 

 that the changes in the jelly during the action of the stain 

 be followed. Then the changes may be followed backward 

 by careful washing of the specimens. 



The presence of two different substances in the gelat- 

 inous covering has been disputed by Hauptfleisch for the 

 Desmids. 



5. Fungus-cellulose. 



283. The membranes of the fungi show very varying 

 relations. In a number of species they give the normal 

 cellulose reactions, and this is especially the case in young" 

 stages (cf. de Bary II, 9). But in most fungi they differ 

 from pure cellulose membranes in being insoluble in cupram- 

 monia and in being colored only yellow or brown by iodine 

 and sulphuric acid or by chloroiodide of zinc. They also 

 show great powers of resistance to alkalies and acids in 

 general. But since, on the other hand, they do not show the 

 reactions for lignification or suberization, we are compelled 



