PHYSIOLOGICAL BOTANY. 237 



pressed on both sides. In the opinion of the author, no 

 doubt can be entertained, after careful examination, that 

 this tube is not closed either at the entrance into the 

 stomata, or lower down, between the cells of the orifice. 

 When it has arrived at the inner termination of the 

 stomatic aperture, this tube dilates into a smaller or 

 larger funnel-shaped expansion, which clothes the inferior 

 surface of the epidermis so far as this bounds the air- 

 cavity externally. This funnel-shaped expansion presents 

 some varieties in different plants, which the author details. 

 Thus the cuticle either lines the walls of the air-cavity 

 only, without penetrating into the intercellular passages, 

 or it penetrates into some, or even all, of those passages 

 which are in connexion with the air-cavity. Lastly, the 

 author comments upon the question of the cuticle being 

 a peculiar membrane, different from the epidermis. He 

 believes that it is not so, but that its peculiarity arises 

 from a change in the substance of the external layers 

 of the epidermal cells themselves. Were I to pass 

 hastily over this paper, as the author says is my custom 

 (although not very politely), I should say that the point 

 is not how the cuticle is formed, but whether it is com- 

 posed of the outer walls of the epidermal cells, and as 

 this has not been shown to be the case, it must be con- 

 sidered as a peculiar membrane until it is so. At all 

 events, the question remains in statu quo. But, as in all 

 questions relating to the formation of organic bodies, we 

 must look forward for a complete elucidation of this point, 

 to a clearer insight than has yet existed. 



Investigations upon the Cellular Structures which Jill 

 up Vessels. By an anonymous Author. Botan. Zeit., 

 1845, p. 225. The author first shows that these bodies 

 consist of true cells, or, as he expresses it, that they are 

 phenomena analogous to the ordinary simple cells of 

 plants. These cells are not generally formed while the 

 plant is young ; in first year's shoots of Vitis vinifera and 

 Sambucus niyra, as also in the stems of Cucurbita pepo, 



