STUDY OF THE GENICULA OF CORALLINE. 37 



sometimes it is free from any packing. These differences depend 

 upon the .species. Tn some species which have no true spaces between 

 the cells, the middle lamalla has a considérable, thickness ; in those 

 which have the rooms, the middle lamella, is found adherent to the 

 primary celhvall around the room. In either case the middle lamella 

 runs into the genicular portion proper, often much compressed at the 

 critical point and hard to detect. The middle lamella at the genicular 

 portion proper is almost always much thinner than in the articular 

 portion. The middle lamella is rich in pectin compound and stains 

 very well with hsematoxylin, safranin, anilin blue and ruthenium 

 red. 



The primary cell wall supplies the greater part of the framework. 

 When the pectin compound had been dissolved by proper treatment, 

 the cellulose reaction was seen in this part. An exception is the cell- 

 wall of the subepidermal layers : it makes no response to the cellulose 

 reagents, but gives us a vivid gélose reaction. 



The primary celhvall of the articular portion is continued to that 

 of the genicular portion proper. It becomes much thinner when it 

 enters the latter portion and seems to assume a chemical character 

 different from the articular portion. This conclusion is reached from 

 its gfivinff no cellulose reaction even after lon<x treatment with the 

 gélose solvent. It is stained a pale blue by anilin blue and faint violet 

 by hematoxylin. Ruthenium red stains it light red. 



The secondary lamella lines the inside of all the cells and has a 

 character similar to the middle lamella against the chemical and the 

 staining reagents. It runs into the genicular portion proper and a 

 secondary thickening takes place to form the tertiary lamella. These 

 two layers are essentially equal in their character and hardly dis- 

 tinguishable in ordinary reagents. But when stained with anilin 

 blue, the inner layer gains the deepest purple colour and is easily 



