90 Mr W. Gardiner, On the constitution [Feb. 11, 



however is himself inclined to believe, that the hardening sub- 

 stances of many of the fungi of a woody character is identical 

 with suberin. Fremy's 1 experiments, as I shall state later on, 

 point to the occurrence of a substance which he calls metacel- 

 luiose, in the tissue of lichens and fungi. Lastly, as before men- 

 tioned, Berg 2 succeeded in isolating lichenin and lichen starch, 

 the latter being thus designated since it turns blue with iodine. 

 We thus have evidence that in fungi as well as in woody and 

 corky tissue the cell-walls consist of a framework of cellulose, 

 and that other substances such as suberin, metacellulose, lichenin 

 and the so-called lichen-starch may also be present. 



Returning now to the consideration of ordinary vegetable cells 

 we find that Von Mohl 3 made the observation that certain cell- 

 walls existed, e.g. endosperm of Cyclamen, which gave a blue 

 colouration with iodine alone, and Schleiden 4 who discovered a 

 similar phenomenon in the horny cells of the cotyledons of Schotia, 

 Hymenaea, Mucuna, and Tamarindus, appropriated to the substance 

 which produced the reaction the name Amyloid. Other instances 

 of cells which turn blue, are afforded by the phloem cells of Ly co- 

 podium 5 , and of the root of Ruscus acideatus 6 , the endosperm 

 cells of Paeonia 7 , Ardisia and Primula 5 , and certain forms of muci- 

 lage, e.g. the mucilage cells of Linseed and Quince seed, and of 

 the parenchyma cells of the peticle of Aucuba Japonica 9 . 



In some of the foregoing instances as in the case of certain 

 young cells observed by Scharcht 10 , a peculiar hydratic condition of 

 the substance of the cell-wall is required, before the production of 

 the blue coloured with iodine and sulphuric acid. To Scharcht 

 also is due the observation which I have myself repeatedly con- 

 firmed with regard to endosperm cells, that very dry tissue will 

 not turn blue until a certain amount of hydration has taken place. 

 Finally Solla 11 noticed that in the young cells of the growing points 

 of Zea, Phaseolus, and Vicia, the cell- walls do not turn blue, but 

 simply remain yellow or brown, when treated with the usual cellulose 

 reagent. 



Of gums and mucilages one can say but little. There seems some 



1 Fremy, Ann. de Sci. Nat. Ser. 6, xin. 1882. 



2 Berg, Zur Kenntniss des in Oetraria islandica vork. Lichenins und iodblauen- 

 den Stoffes. Diss. Dorpat, 1872. 



3 Von Mohl, Vermischte Schriften, p. 335. 



4 Schleiden, Grundz. der wiss. Botanik. 3rd edition, i. p. 172, &c. 



5 De Bary, Vergl. Anatomie, p. 364. 



6 Gardiner. Besembles in reaction the phloem of Lycopodimn. 



7 Vines (unpublished observation). Mentioned as such in my paper in the Phil. 

 Trans. 1883. The pbenomenon is also referred to in Trelease's English translation 

 of Poulsen's Microchemie, p. 174, 1884. 



8 Gardiner, Phil. Trans. Part in. 1883. 



9 Gardiner. See present paper. 10 Scharcht, loc. cit. p. 72. 



11 Solla, Osterr. Bot. Zeitschrift, 1879, p. 351. 



