1884.] of the cell-wall and middle-lamella. 97 



starch), the mucilage of Linseed, and the phloem cells of Lyco- 

 podium, and of the root of Ruscus aculeatus must, probably, be 

 regarded as consisting of an hydrated cellulose naturally pro- 

 duced, whereas with regard to the cells which turn blue only after 

 the action of acid, such hydration is induced artificially. 



There are some definite grounds also for believing that the 

 so-called fungus cellulose (metacellulose of Fre'my) consists of a 

 form of hydrated cellulose, since Masing 1 showed that in the con- 

 version of cellulose into glucose, the cellulose of fungi underwent 

 the change much more rapidly than that of flax fibre. We know 

 of course that this conversion is simply a process of hydration. 



Just as cellulose walls consist mainly of a definite body — 

 cellulose — so it seems probable from the researches of Fre'my, 

 and in the opinion of such a well qualified chemist as Dragendorff 2 , 

 that in lignified tissue a definite substance — lignin, occurs. At 

 present however we have but few facts to go upon. The difficulties 

 attending its isolation are so great, that it appears somewhat 

 questionable whether the real body has as yet been obtained pure, 

 and unacted upon by reagents, and knowing as we do the difficul- 

 ties attending the separation from it, of foreign substances, we 

 must as yet regard with some doubt, researches such as those of 

 Erdmann 3 and Bente 4 on pine wood, which would tend; either to 

 show that in lignified cell- walls the cellulose and lignin are chemi- 

 cally combined as glycolignose ; or that lignin, as such, actually 

 yields pyrocatechin as a product of its decomposition ; thus point- 

 ing to its relations with the benzol series. In fact although certain 

 of its reactions may, and probably do, point to the existence of a 

 definite body yet that* body has most probably not yet been 

 isolated. 



Of cutin one has but little to say. As has been already remarked 

 the suberin of Von Hohnel has been shown by Fremy to consist of 

 a mixture of cutin and lignin, and that it is from the cutin that 

 the suberic acid is derived. In corky as in lignified cells a frame- 

 work of cellulose is always present which although it may or may 

 not be directly obvious, can always be shown to exist after the 

 action of Schultze v s mixture in which both the lignin and cutin 

 are soluble 5 . 



Dealing now with mucilages one must confess at the outset 

 that the chemistry of these substances is still in a most un- 

 satisfactory state. Nor is this to be wondered at. Leaving out of 



1 Masing, Pharm. Zeitschr. f. Russland, rx, 385, 1870. 



2 Dragendorff, loc. cit. p. 253. 



3 Erdmann, Annal. d. Ghem. u. Pharm. cxxxvin. 1, 1866. 



4 Bente, Ber. d. d. chem. Ges. xin. 476, 1875. 



5 Lemaire, Ann. Set. Nat. xv. (1883), p. 297, finds that in certain cases, e.g. 

 the Cycadeae, the epidermis itself has undergone lignification. 



VOL. V. PT. II. 7 



