PREFACE. Vll 



Mr. Jenner and myself have used Mr. Ross's microscopes, 

 and I think it due to that skilful optician to state, that for 

 clearness of vision we have never seen them surpassed. 



I have added, as an Appendix, a list of as many foreign 

 species as have come to my knowledge ; and, although I 

 fear that a few of Ehrenberg's may have been omitted, I have 

 some confidence that this work describes and figures a greater 

 number of species than have before been systematically 

 arranged. M. de Brebisson and Professor Bailey have kindly 

 permitted me to insert species which they have recently de- 

 tected, and which are now first published, and also to make 

 use of their drawings. The last plate has been reserved for 

 these drawings and for others which Professor Kiitzing has 

 presented me of species which he has described but not 

 figured. I have to regret that the large size of the Closteria 

 did not allow the introduction of figures of several interesting 

 foreign species. 



The drawings of the British species, with very few ex- 

 ceptions, were made by Mr. Jenner ; but they have, in almost 

 every instance, been carefully re-examined by myself and 

 compared with the plants, and the engravings have been 

 executed under my own superintendence. From the com- 

 mencement of this undertaking Mr. Jenner's help has been 

 invaluable. Not only has he taken the greatest pains to 

 ensure the accuracy of the drawings and furnished me with 

 copious notes, but to his exertions I owe a very large pro- 

 portion of my Subscribers. Indeed I can truly say that he 

 has shown as great an interest in the work as if it were his 

 own, and exerted himself as much for me as he would have 

 done for himself. 



To the kind recommendations of Mr. Bowerbank, who is 



