Ill 



rounded with runners, while others exhibit none ; the first ap- 

 pear to have been grown from cuttings, the latter from seed. 



The subterranean herbaceous stem differs much more from 

 the air stem than was the case in the arborescent ones above 

 mentioned ; under this head are reckoned the anamorphoses 

 of the stem, which have hitherto been described under the 

 names of rhizoma, radix repens, bulbus, tuber, &c. Our au- 

 thor lays down three kinds of this subterranean herbaceous 

 stem; in the first the creeping stem does not increase in 

 thickness, in the second it does, and in the third kind the 

 stem is erect. He also directs attention to the circumstance, 

 that at times the terminal bud in the subterranean stem grows 

 further horizontally, while the lateral buds are developed in 

 the form of air stems in a vertical direction, and then the air 

 stem frequently takes a horizontal direction. A number of 

 excellent examples are enumerated ins upport of the three 

 positions. 



The inquiries relative to the difference between root and 

 stem also abound in interesting observations. 



A learned correspondence has begun between E. Meyer and 

 H. Mohl*, which promises to explain some of the most diffi- 

 cult points of morphology ; it relates to the morphological 

 signification of fibres, which E. Meyer considers, from their 

 position, analogous with branches. 



M. Mohl perfectly coincides with E. Meyer respecting the 

 origin of the stem from leaves, but he does not adopt Meyer's 

 view of the formation of nodes, any more than the statement, 

 that the collum of the plant should be regarded as the first 

 node, and that to each internode would belong the node si- 

 tuated at its lower extremity, which are victoriously contested. 

 It is incomprehensible to me how M. Mohl can dispute this 

 latter statement, agreeing as he does to the first, on the origin 

 of the stem from leaves, for it appears that the one proceeds 

 from the other ; in my opinion, observation shows that the 

 leaves shoot forth from the stem, and this therefore cannot 

 consist of the cohering leaves or petioles. 



M. Mohl regards the fibre as an axis which originates from 

 a descending current of sap, and merely represents the lower 

 portion of the vascular bundle of a perfect axis 5 as on the 

 * Linnoea, for 1837, pp. 106, 487. 



