



















• 













IN VEGETABLE BIOLOGY. 



529 



Chestnut. Abundance of this kind of tannin in the cells of the 

 bud-scales. 



The chief value of Nessler's fluid to the microscopist is that, 

 apparently in consequence of the rapid difFusibility of caustic 

 potash, its action in showing up any tannin- containing cells in a 

 tissue is very quick. This valuable property is alluded to among 

 the further details to be now given. 







































- 



. 





* 



■ 





■ 



Group I. Primrose epiderm. — To see the tannin in this plant, 

 the easiest way is to tear off pieces of epiderm from the under- 

 side of the leaf, and mount them in the testing-fluid. The strips 

 should include some cells overlying a vascular bundle. With 

 -Nessler's fluid one immediately sees that tannin idioblasts are 

 present in some numbers in the elongated cells overlying the 

 vascular bundles, and from the very dark, frequently quite black, 

 colour of the precipitate, the richness of these elements in tannin 

 is manifest. Numerous tannin idioblasts are, as has already been 

 mentioned, scattered among the ordinary epidermal cells : the 

 latter contain a nucleus and numerous chlorophyll corpuscles, 

 which, contrary to what is usually the case, are about the same 

 size as those of the guard-cells. The guard-cells give no sign of 

 tannin, and it is rather rare to find tannin idioblasts bordering on 

 them * The hairs covering the leaves consist of a simple row of 

 cells, and show a curious disposition of the tannin ; as a rule, the 

 alternate cells are tannigerous, the intervening ones have chlo- 

 rophyll and are without tannin ; the proximal cell of the hair 

 may have tannin, or be a chlorophyll-cell 



Besides Nessler's fluid, the only ordinary reagent able to 

 show up the tannin of the Primrose without any loss of time is 

 osmic acid in 1-per-cent. solution, which causes the well-known 

 mky-blue precipitate to be thrown down in the taanin elements. 





tannin 



































; 













■ 



L 









■ 



cells in such a case as Primrose epiderm, if the ordinary tests are 

 used, the following Table is subjoined. 



beat 



At 



tannin 



>phyll disapp 



of the smaller number 

 ears from them. 

















. 





. 







: 









' 



' 









M 





















■ 





