839 



and consequently with the most contradictory views ; thus for ex- 

 ample, opinions are still quite divided regarding the doctrines of the 

 development of the cell, of the origin of the embryo, and of the exist- 

 ence of an impregnation in the higher Cryptogams. Both in these 

 and in other cases, the small compass of the present treatise forbids a 

 more extensive detail of the researches upon which the opposing 

 views are founded ; I hope, however, that I have succeeded in making 

 clearly prominent, the chief points upon which these contests turn, 

 and thus, in facilitating the formation of a judgment by the reader; 

 and, I have never neglected to indicate the literature from which fur- 

 ther instruction is to be derived." 



As it is quite impossible to give either an analysis or abstract of 

 the essay introduced to the English reader by the foregoing Preface, 

 we think that we cannot do better than assure our readers that they 

 ought to possess themselves of so valuable a contribution to the sci- 

 ence of phyto-physiology. We select for extract a passage on a sub- 

 ject of immediate, although not evanescent, interest. This, while 

 bringing the moot question of cryptogamic reproduction instructively 

 and lucidly before the reader, will also serve as a fair example of the 

 matter and manner of this acceptable volume. 



*' Propagation of the Cryptogams having Stem and Leaves. — While 

 in the three families of Cryptogamia possessing a thallus (with the 

 exception of the Charas, to be mentioned presently), all attempts to 

 discover male organs have proved the more vain the further the inves- 

 tigation of these plants has advanced, in the more highly organized 

 families of Cryptogamia, on the contrary, in which there exists sepa- 

 ration of the organs of vegetation into stem and leaf, the last few 

 years have seen the discovery of convincing proofs of the existence 

 of two sexes. 



" In the last century, when Hedwig in particular devoted himself 

 to the investigation of the Cryptogamia, the idea that two sexes must 

 exist in all Cryptogamous plants, was quite predominant; and thus 

 often enough without a trace of consideration, the most diverse parts 

 were, from mere opinion, separated as male organs. This brought the 

 whole effort to discover impregnating organs into discredit, and the 

 opinion that all the Cryptogamia were devoid of male organs, and 

 developed their spores without previous impregnation, became more 

 and more diffused. It is true that organs had been discovered in 

 certain Cryptogamous families, especially the Charas and Mosses, 

 which from the time of their appearance, from their position &c. 

 stood in evident relation to the fruit ; but since no positive influence 



