352 Messrs. Cross and Bevan on the Correlation of 



astringent substances has been already established*; and the 

 latter have been assumed by physiologists to be residues of 

 the oxidation of carbohydrates. In regard to the lignifica- 

 tion of structures originally consisting of pure cellulose, we 

 have two alternative hypotheses to account for the change: — 

 (1) that it results from an intrinsic modification of the cellu- 

 lose itself effected in situ ; and (2) that it is the result of com- 

 bination of cellulose with aromatic bodies formed elsewhere 

 in the plant, and probably as residues from the oxidation of 

 carbohydrates. There is perhaps more negative evidence on 

 the subject of the second than there is positive in favour of 

 the first hypothesis ; and the difficulties which beset the eluci- 

 dation of the question are an apt illustration of the limitations 

 which impede the solution of the chemical phenomena of life. 

 If the cellulose combine with astringent substances presented 

 in solution, to form insoluble products, these may be assumed 

 to resemble those compounds which form the basis of the 

 dyeing of the cellulose fibres. A superficial study of any of 

 the non-cellulose or lignified fibres will satisfy the observer 

 that they behave rather as modified celluloses than as a com- 

 pound of the above weak order. In the first place, the reso- 

 lution of the fibre-substance of lignified fibres can only be 

 effected by means of drastic reagents, whereas a compound of 

 cellulose with a body that it has merely removed from solution 

 (that is to say, in what we may term adhesive combination) 

 is always easily decomposed. We have further made a series 

 of observations upon seedlings, which show that the astringent 

 substances formed during germination are present in the 

 juices and yet absent from the substance of the fibro-vascular 

 bundles. Again, if lignification followed the course in ques- 

 tion, it is difficult to account for the comparatively invariable 

 composition of bast-fibres. Not only are they remarkably 

 uniform in composition from end to end, but they may be 

 obtained white and lustrous by a process of bleaching which 

 occasions a minimum loss of weight ; they may be converted 

 into explosive nitro-compounds, an examination of which 

 shows them to be homogeneous ; they are soluble in the 

 ammonio-cupric reagent, a property which has been denied to 

 them by certain observers ; and the precipitate obtained on 

 adding an acid is simply the amorphous modification of the 

 originally organized fibre-substance. The characteristic yel- 

 low coloration moreover which lignified fibres give when 

 treated with a solution of aniline sulphate, and upon which 

 much stress has been laid as distinguishing them from the 



* Sachs, Handb. der exper. Phys. (1865; pp. 361-369 ; Sachse, Farbstofe 

 &c. (1877), p. 113; Cross and Bevan, Cbeni. Soc. Jourri. xli. p. 90, 



