1884.] of the cell-wall and middle lamella. 8D 



Woody and sclerenchymatous tissue also, after being treated with 

 nitric acid and potash, reacted in the usual manner towards cellu- 

 lose tests. Similarly as regards the cuticle, Hofmeister 1 found 

 that after three weeks maceration in potash, the insoluble remain- 

 ing skeleton became distinctly blue with a solution of iodine. 

 Thus in every instance a cellulose framework apparently remains. 

 The lignin, cutin, suberin and the like, must however be regarded, 

 not as infiltrated substances, to be placed in the same category 

 with such bodies as silica 2 , or iron 3 , but rather as portions of the 

 cellulose which have experienced chemical change. In the present 

 state of the science we know but little as to how these changes 

 occur, but it is a matter of interest to observe that they can take 

 place only in the living plant, although as it appears, in the 

 conifers at least, the cells may have lost their cell-contents 4 . 



Besides these fairly well defined modifications of cellulose 

 which accompany lignification, cuticularisation, or the formation of 

 cork, we have yet to consider other forms of cell-wall, which may 

 be conveniently separated from the foregoing. Sometime after 

 Payen's 5 discovery that cell-walls turned blue when treated with 

 iodine and sulphuric acid, Scharcht 6 showed that the walls of 

 certain fungi, even after treatment with potash, did not give the 

 reactions of cellulose, but with iodine and sulphuric acid were 

 merely stained yellow. In consequence of this observation, the 

 walls were regarded as consisting of a definite form of cellulose, 

 which was known as the fungin of Braconnot 7 , or the fungus 

 cellulose of de Bary 8 . Richter 9 however is of opinion that a 

 definite fungus cellulose does not exist, but that the walls in 

 reality consist of ordinary cellulose together with a body, which 

 in certain fungi, e.g. Daedalea, he makes out to be suberin 10 . He 

 found that when fungus-tissue was treated for some time — in 

 certain cases, several weeks — with solution of potash, washed 

 with weak acid, and mounted in chlor. zinc, iod., the customary 

 blue colouration was obtained. However, as Dragendorff 11 points 

 out, one cannot with certainty make deductions with regard to 

 results produced after such lengthy action of potash, and conse- 

 quently, one must not regard them as quite decisive. Dragendorff 12 



I Hofmeister, PflanzenzeUe, p. 257. 2 Von Mohl, Bot. Zeit. 1861. 



3 Weiss u. Wiesner, Sitzber. d. k. Akad. in Wien, xl. 1860. 



4 Strasburger, Der Zellhailte, p. 199. 5 Payen, loc. cit. 1811. 



6 Scharcht, Die PflanzenzeUe, 1852. 7 Braconnot. See Fremy, I. c. 



8 De Bary, Morphologie der Pilze, Flechten u. Myxomyceten. (Hofmeister, 

 Handb. d. phys. Bot. n. p. 7 u. ff.) 



9 Bichter, Sitzber. d. k. Akad. in Wien, lxxxiii. 1881. 



10 In the mushrooms he believes that a substance of a proteid nature is present 

 together with the cellulose. 



II Dragendorff, Plant Analysis, English translation, 1884, p. 257. 

 12 Dragendorff, loc. cit. p. 255. 



