Manchester Memoirs, Vol. xlv. (1901), No. 1. 11 



experimental researches has established that the diffusion 

 of salts takes place as rapidly in gelatinous masses as in 

 water. A more readily permeable cell wall might very 

 easily account for the greater simplicity of the phloem 

 cells and for the reduction of the sieve plates. 



Now, in view of the relationship of the Lepidodendracece 

 with the existing Lycopodiacca;, it seems not unlikely that 

 the fossil ancestors or allies of this group of plants 

 had phloem elements with walls of the same amyloid 

 substance, and this must, I think, be taken as the cause 

 of the great difficulty of preservation of this tissue and 

 the frequent absence of all structure from the phloem 

 region even when such delicate tissues as the cambium 

 and the mid cortex were preserved. 



For amyloid, such as it exists in the seeds of some 

 leguminous plants, is of so mucilaginous a nature that it 

 dissolves in boiling water and is partly soluble in cold. 

 In the case of the Lycopodia though 1 could not get any 

 solution of the cell walls in hot water, yet they swelled 

 up considerably, so that we are dealing probably with a 

 more resistant variety of this substance though one which 

 is much more readily acted upon than cellulose.^ 



Gilson,2 in his memoir on the chemical composition of 

 the vegetable cell wall shows that probably there are two 

 such varieties of amyloid, one more easily soluble in water 

 and the other not readily soluble. Probably amyloid stored 

 as food material is of the former category, while amyloid 

 forming the cell walls of conducting cells is of the second 

 category. Still even this more resistant variety would be 

 more yielding than a cellulose wall, and if in breaking 

 down it formed mucilage, as seems likely, it would swell 

 up with water, and this might account for the fact that the 



^ Cross and Bevan. Celhdose, p. 224. 



2 Gilson E. La Cellule IX. 2« fascicule, 1893. 



