VON MOHUS VEGETABLE CELL. 57 



acid In plants is a true physiological function, intimately con- 

 nected with the life of the plant ; and that this (rather than 

 the opposite and predominant nutrient process, through which 

 carbonic acid is decomposed and oxygen evolved) should be 

 considered as the respiration of plants, if we use the term at 

 all (p. 86). "The roots of plants, and not the leaves, take 

 up the substances which furnish plants with nitrogen, while, 

 on the contrary, the leaves play the essentially active part in 

 the absorption of carbonic acid " (p. 88). The analogy of 

 the milky juice of plants to the blood of animals, as pro- 

 pounded by Schultz, is thoroughly refuted by our author, and 

 the flowing movement in the milk-vessels described by Schultz 

 is positively denied to take place in an uninjured plant, except 

 as produced by mechanical causes. That the milky juice is 

 not a nutrient material, still less the nutrient juice, is also 

 manifest (p. 96). 



The cell as an organ of propagation is treated, first, as 

 respects the multiplication of plants by division ; second, by 

 spores ; and third, by seeds. The conjugation of certain 

 Confervoid Algce, such as Zygnema, is said to bear no anal- 

 ogy to sexual reproduction (p. 113) ; a conclusion which may 

 be questioned. A good summary is given of the facts known 

 respecting the free and spontaneous movements of the spores 

 of the lowev Algce (p. 115) ; and also of the recent discoveries 

 respecting the bisexual reproduction of the higher Grypto- 

 gamia. 



The reprint of Henfrey's Report, in the January and 

 March numbers of this Journal, has placed our readers au 

 courant with the present state of knowledge on this intei-esting 

 subject. It should be noticed that Mohl denies the existence 

 of antheridia in lower Cryptogamia^ or Thallophytes ; but 

 maintains that the small bodies, moving by two cilia, discov- 

 ered by Decaisne and Thuret in the Fucacece^ are more prop- 

 erly a second kind of spores, analogous to the small spores 

 of the Floridem^ than of the nature of the seminal filaments 

 of Ferns, Mosses, etc. (p. 117). The latter researches of 

 Itzigsohn, Thuret, Tulasne, etc., however, lead rather to the 

 conclusion that the lower Cryptogamia (except the very low- 



