230 PHYSIOLOGICAL BOTANY. 



of the pith of the recently- developed twigs of the willow 

 (e. g.) this mass assumes a tolerably compact form ; in 

 twigs of a year's growth it is found diffused, and has 

 formed dotted cells. Now it appears to me, that this 

 membrane becomes applied whilst in a delicate state to 

 the wall of the cell, and in certain parts penetrates more 

 deeply through the secondary deposit, until it reaches 

 the outermost membrane, and in this manner the appa- 

 rent holes or pits are produced. The prominences seen 

 on the utricle after it has been detached by nitric acid, 

 and which fit into depressions in the membrane of the 

 cell, and the elevations between them, appear to prove 

 this to be the case. The nitric acid probably only acts 

 by contracting the parts and rendering them visible. 

 The membrane inclosing the granular contents, when 

 detached from the walls of the cell, is only rendered of a 

 pale yellow colour by iodine, and at first is not at all 

 coloured by it. Prom these considerations, it appears 

 clear to me that this membrane is applied to the outer 

 membrane of the cells, and that it is again detached from 

 it by the action of nitric acid, but for this very reason it 

 cannot be a primordial utricle. 



UNGER'S Memoir in the ' Botanisch. Zeit.,' 1844, 

 s. 498 et seq., upon the Growth of Internodes anato- 

 mically considered, properly belongs here. The author 

 counted the internodial cells existing in Campelia Za- 

 nonia, and then compared the number with their 

 length and breadth, whence he arrived at the conclu- 

 sion, that the enlargement of the internodes is the result 

 of the continuous growth of the new elementary parts, 

 and also that the enlargement of the internodes of the 

 axis arises from both the addition of new elementary 

 parts and the increase of those already existing. He 

 then goes further, and proposes the question of how, and 

 in what manner, the addition of new elementary organs 

 (cells) takes place in the growth of the internodes. He 

 examined a longitudinal section which passed through 

 several internodes, and then found that the formation of 



