EXTRACTS AND ABSTRACTS FROM FOREIGN JOURNALS. 209 



had even a power of locomotion, confined, however, to a very small 

 compass. In the vertical position they assumed the appearance of 

 black points, so that at first he supposed two sorts of sporules to be pre- 

 sent, until, upon closer examination, he remarked that the change in 

 the aspect under which he viewed them gave rise to this deceptive ap- 

 perance. 



He mounted some of these bodies in the manner described by M. 

 Oschatz, and on 20th of November, or nearly eight weeks afterwards, 

 the motion still continued as active as at first. Specimens of this plant, 

 which had been collected in 1822, upon being macerated in water, 

 afforded the same phenomena, although the motions were certainly less 

 active. 



[From the Annales des Sciences Naturelles, April, 1842.] 



Unger on the Origin of Spiral Vessels. In the plant just emerging 

 from the embryo condition, in which state only can the examination 

 be made, there are two parts especially, the exact study of which throws 

 the most light upon the development of the spiral vessels. 



These two points are the summits of the stalks, with the buds and 

 the extremities of the principal and of the lateral roots, in other words, 

 the two poles of the vegetable axis. 



Before entering, however, into the details of this subject, it is neces- 

 sary to understand fully the meaning of the expression spiral vessels, 

 very different views in this respect having been entertained by au- 

 thors. 



In the sense attached to it by the old phytotomists, two sorts of 

 organs are included ; the one of which is distinguished by the presence 

 of annular or spiral fibres, and is in the form of a simple annular or 

 spiral vessel ; whilst the other, instead of simple fibres, has them larger 

 and more ramified, giving, in consequence, to the vascular membrane, a 

 reticulated or sieve-like appearance; vessels of this kind have been 

 denominated reticulated or striated, and of them the true porous ones 

 are only a modification. 



Since all these fibrous tissues are not found, as asserted by Meyen, in 

 the original formation of the vascular wall, but only become deposited 

 at a later period, on the originally homogeneous membrane of that part, 

 it necessarily results, that all the forms of vessels above mentioned, 

 originate in a similar manner, as far as regards the more essential 

 points. 



Direct observation, and the comparison of younger formations with 

 those more advanced, indicate that the fibrous tissues belong, in some 

 way, to a secondary layer, deposited on the primitive membrane of the 

 vessel, and determine the manner in which this increase in the thick- 

 ness takes place. 



From this it appears certain, that the spiral vessels are not truly 

 elementary organs, but that they are on the contrary composed of nume- 

 rous cells, superimposed perpendicularly, and more or less cylindrical or 



VOL. II. P 



