58 REVIEWS. 



est) are likewise bisexual.^ Under the head of Eeproduction 

 by Seeds, Mohl gives an interesting and critical account of the 

 development and structure of the pollen and the ovule, and of 

 the origin of the embryo. The latter arises by cell-multipli- 

 cation of the germinal vesicle, a cell produced by free cell- 

 formation in the embryo-sac usually before the pollen-tube has 

 reached the latter. The germinal vesicle and the extremity 

 of the pollen-tube are separated by the thickness of the parie- 

 ties of the embryo-sac. The penetration of the pollen-tube 

 into the latter or into an introverted portion of it, and the 

 formation of the embryo from the apex of the pollen-tube 

 itself, as taught by Schleiden, are wholl}^ repudiated ; and 

 indeed the Schleidenian doctrine may now be considered as 

 thoroughly demolished, by the direct observations of Amici, 

 Mohl, Muller, Hofmeister, Unger, Henfrey, and Tulasne. 

 The Cell as an Organ of Motion is considered as respects move- 

 ments of individual cells through the agency of vibratile cilia, 

 as respects the directions and curvature assumed by organs, 

 and as respects movements by irritation of stimuli, etc., giving 

 an excellent summary of our knowledge on these points, with 

 much admirable criticism ; which want of space prevents us 

 from noticing in detail. 



1 Itzigsohn in Botanische Zeitung, May, 1850. — Here it is announced 

 that the hlack clots on the surface of the frond of Burrea ciliaris contain 

 antheridia, that is, cells from which escape animalcular-like corpuscles 

 that move freely in water, and are similar to those of Mosses and Liver- 

 worts. Later, after stating that others had failed to detect those move- 

 ments, he announces that they had been observed by Rabenhorst, after 

 many ineffectual trials. He also (December, 1850, February, 1851) 

 states that these " spermatozoids " do not manifest viral movements until 

 after the maceration of the Lichen in water for several days. 



Tulasne {L. R.) Memoire pour servir a VHistoire Organographique et 

 Physiologique des Lichenes ; in Ann. Sciences Naturelles, 3 ser., xviii., No. 

 1, 2, 3, 4 (1852), with 16 plates. — A most admirable and complete 

 memoir, elucidating in an unequalled manner the whole structure and 

 morphology of the Lichens. It is to be hoped that the author will publish 

 it in a separate form, as it introduces a new era in Lichenography. On 

 the subject of the so-called antheridia (which alone we can here notice), 

 M. Tulasne has recognized the universal occurrence of these bodies in 

 Lichens, has ascertained their structure and development ; but he has 

 never detected any free movement of the corpuscles, except the general 



