262 STUDIES IN VEGETABLE BIOLOGY. 



and caustic potash, and Gnezda's test for proteids, which fail with 

 eell-w r alls, fail too with catechu. 



3. The behaviour of lignified cell-walls to various reagents 

 proves the existence in them of an iron-greening tannin : this is 

 confirmed by the similar action of various staining fluids upon 

 tannin in the plant and upon the cell-walls. In the meristem 

 of the stem of Isoetes lacustris there is an iron-greening tannin, 

 while an iron-blueing tannin shows itself in the Do£-Kose — best 

 in the collenchyma. The hard bast of the Fig has in its walls a 

 glucoside (possibly an iron-greening tannin) to which some 

 peculiar reactions are to be referred. 



4. That the proteid and other reactions of cell-walls depend 

 upon the presence therein of glucosides can sometimes be proved ; 

 but in the case of ordinary lignified walls this is rendered diffi- 

 cult by the appearance, in them, of a red colour on boiling with 

 dilute hydrochloric acid. This red colour is probably some 

 decomposition-product of an iron-greening tannin, for a similar 

 colour is got when a solution of catechu is boiled with dilute acid. 



5. The failure of the cell-walls to take up carmine and aniline- 

 blue is what should not happen supposing them to contain 

 proteid. But no form of tannin will take up carmine in the 

 plant, and iron-greening tannin will not stain with aniline-blue. 



6. The presence of glucoside in lignified cell-walls may possibly 

 give to them their property of conducting fluid, a propos of 

 Haberlaudt's discovery of a glucoside as the osmotically active 

 substance in Himosa putlica. In meristems the fundamental 

 tissues and soft bast tannin is probably transmigratory. 



7. The precisely similar colour taken with methyl-green by 

 lignified cell-walls and by the nucleus suggests the possibility of 

 an iron-greening tannin being present in the latter. 



8. It is doubtful whether proteids occur in the latex of the 

 Fig, since the proteid reactions yielded by it may well be due to 

 an iron-greening tannin, the presence of which in latex is pro- 

 claimed by a number of tests besides those by which proteids are 

 known. 





