136 Bibliographical Notices. 



of Algae, and defined many new genera, which have been for the most 

 part adopted ; and had he carried on his botanical pursuits to a still 

 more recent period, when the improvement of the microscope would 

 have corrected many points in regard of minute structure which 

 were scarcely before within the grasp of the observer, there can be 

 no doubt that he would have ranked as one of the first algologists 

 of the day. He commenced too a series of correct illustrations of 

 Diatomacece, but his observations in this direction, though the most 

 valuable which had then appeared, seem to have been checked by 

 growing notions of the animal nature of the lower Alga?. The 

 neighbouring group of Desmidiete, though containing some of the most 

 curious and beautiful forms in nature, had all along, with very few 

 exceptions, been unaccountably passed by without examination. 

 Turpin's and Meyen's observations were neglected or disbelieved, 

 while Kutzing's, Meneghini's, and above all Brebisson's treatises seem 

 to have been almost unknown. The memoirs of the two former 

 indeed were accessible enough, but the credit attached in this country 

 to Ehrenberg's notions as to the animal nature of these bodies seems 

 very much to have turned aside the attention of botanists from them, 

 while they were not adopted by the zoologists, but were left to be 

 admired and then laid aside by the mere microscopist. 



Such very nearly was the state of the subject when the Diato- 

 macece and Desmidiets were taken up by Mr. Ralfs, who was perhaps 

 the first botanist in England who fully felt the necessity, not merely 

 of ascertaining the general appearance of the threads or frustules as 

 seen immediately under the microscope, but of understanding the 

 form of their sections with a view to the complete development of 

 their structure. This, with the older microscopes, was almost im- 

 possible, as the utmost clearness and definition of outline is neces- 

 sary for this point, and even with all modern helps and appliances 

 the necessary manipulation is difficult enough. Mr. Ralfs however 

 was no less gifted with tact than perseverance, and thus some of the 

 most anomalous appearances were resolved into very simple pheno- 

 mena. In the course of his observations he found daily more and 

 more reason to believe in the vegetable nature, more especially of the 

 Desmidiea, a belief as regards the latter amounting at last to per- 

 fect conviction from the discovery, peculiarly his own, except as re- 

 garded the long anomalous Closteria, of a mode of propagation, ex- 

 tending through the whole group, by means of the conjugation of 

 distinct individuals after the manner of the Conjugates. Mr. Thwaites, 

 whose interesting discoveries have already been recorded in our 

 Journal, has now extended this to Diatomacea, so that, together with 

 the Corallines, there is at the present period no doubt, except as re- 

 gards one or two Hamatococci, of the vegetable nature of the whole 

 order of Alga?. 



But not only has this discovery thrown light upon the real affini- 

 ties of these productions, but as regards generic and specific distinc- 

 tions it is of no less importance, for strongly as the mode of conju- 

 gation resembles that of Zygnema and its allies, the mode of propa- 

 gation and indeed the actual physical value of the bodies is not the 



