STRUCTURE.] 



ORGANIC MUCUS CAMBIUM. 



membrane, applied to the surface of the leaves of some plants, 

 and only separable after maceration ; it is probable that it 

 constitutes the whole exterior coating of all plants ; it is cer- 

 tainly drawn over the sacs which constitute hairs j I have 

 found it distinctly on the petals of Hydrotsenia Meleagris 

 (see Bot. Reg. 1838. misc. No. 128), but its extreme tenuity 

 and firm adhesion to the tissue below it renders it difficult to 

 detect it ; and there is no doubt that it occurs very generally 

 in the interior of plants between their cells, filling up the 

 intercellular spaces, and gluing together all the parts. Mohl, 

 with his usual skill, has shown that this substance is found 

 so frequently, that we cannot refuse to acknowledge its 

 presence as a constant fact. The Box, and the young annual 

 shoots of Sambucus nigra, are especially noticed as well suited 

 to show this structure ; it will be seen to form a considerable 

 part of the mass of the albumen of Alstromeria Salsilla, see 

 fig. 2. c. where it is ^^ of an inch in diameter. Valentin 

 has measured the thickness of the intercellular organic mucus 

 in several instances, and gives the following table of the pro- 

 portion between it and the cells of certain plants, calculated 

 in Paris inches. 



Meyen admits the fact of the presence of this intercellular 

 mucus, and considers it a secretion from the sides of the cells. 

 He particularly refers to its condition in the petiole of Beta 

 cycla, in proof of the correctness of that view. 



No doubt can be entertained that it is of universal occur- 

 rence between the cells or tubes of all vegetable fabrics. 



Cambium, as it is called, originally observed at the sepa- 

 ration of the bark and wood of Exogens, in the spring, seems 



