vi PREFACE. 



That the Author possesses a grasp of the historical 

 development of the subject has already been evidenced in 

 his previous treatises, and the same feature often appears 

 in the present volume. 



In the majority of the Text-books and Manuals pub- 

 lished in recent years, great confusion exists with regard 

 to the appending of authors' names to the Illustrations. 

 In one and the same book, for example, we meet with 

 instances where the name of the author of the original 

 work whence the copy has been taken is given as it 

 should be and also with other cases where the actual 

 author is ignored, his name being replaced by that 

 of the compiler of some text-book from which the copy 

 was obtained i.e. some one who himself has done no- 

 thing more than copy. Such a mode of- procedure is 

 in a high degree calculated to produce a misty conception 

 of the actual circumstances in the mind of the reader, the 

 more so because, as stated, no importance is attached to 

 the occurrence. DR. LAFAR has, however, set vigorously 

 to work to combat this bad habit by taking all his 

 reproductions direct from the original sources, so that 

 they are clear and accurate representations of these ori- 

 ginals. 



The subjects included in the present work have been 

 dealt with in a many-sided manner, the Botanical as well 

 as the Technical and Chemical aspects having been borne 

 in mind, although preference has throughout been accorded 

 to the two latter. The style is flowing and clear, in many 

 places lively and picturesque, and I have read with interest 

 even those portions wherein I am not at one with the 

 opinions of the author. The attention devoted to the most 

 recent developments of the subject gives a special value to 

 the book. 



Within the last two decades the study of Microbiology 

 has made gigantic strides, both in the pathological and the 

 technical branches of the subject ; and just as investigations 

 into the Physiology of the higher plants gave the first im- 



