28o Phillips on a Comparative Study of the 



iodine and sulphuric acid. As it grows older it loses this 

 property, apparently from its being changed, or impreg- 

 nated by some substance which is negative to all cellulose 

 tests. It seems to be allied to fungus-cellulose, though 

 Macchiati (50) considered it and the sheath to be the same 

 as the cuticle of the higher plants. Correns (18) was able 

 to get a cuticular reaction for it with an alcoholic solution of 

 chlorophyll. The present investigation gave no reaction 

 sufficiently marked to warrant the substance being termed 

 cuticle, though the two may have close affinities. 



The walls are laid down in distinct lamellae by the addi- 

 tion of microsomata of cellulose upon their inner faces. 

 Ambronn ( i ) found that there was a substance between 

 the lamina of cuticular sheaths which disappeared upon boil- 

 ing and reappeared when the plant was cooled. He, there- 

 fore, concluded that the substance had melted. Hegler (38) 

 found that the laminae retained their identity when heated 

 in glycerin until the boiling point of the fluid was reached, 

 which is much higher than that of water. In such forms as 

 Nostoc, Anahaena, etc., all of the lamellae, except the one 

 immediately enclosing the protoplast and possibly at times 

 a second, swell up and become a thick gelatinous protective 

 zone. If a little care be taken in crushing out the colonies 

 of Nostoc, this zone can easily be traced to consist of the 

 successive generations of lamellae, thus the inner unswollen 

 wall which was formed last invests but a single cell. The 

 one immediately outside it invests two cells, while the others 

 in order will invest respectively four, eight and sixteen cells 

 each. When these swollen sheaths are knotted up together 

 they make the apparently homogeneous jelly of the Nostoc 

 colony. 



In some forms, as Lynghya, the outer sheaths do not 

 gelatinize, but remain tough and thin. If Lynghya be culti- 

 vated in a weak solution of palladious chloride (i : 100,000) 

 or in platinum chloride of the same strength, this laminated 

 structure is beautifully demonstrated, and the laminae are 



