PREFACE. 



The preparation of the present volume was begun by the author in the year 

 1865, after the other contributors to the Handbook, who had originally undertaken it, 

 had retired. It was fairly far advanced, when in 1867, by reason of other necessary 

 business, it had to be put entirely on one side for almost two years. It also suffered 

 frequent and long interruption at a later time through changes in the official engage- 

 ments of the author. 



The object of the work, as stated in the programme of the Handbook, was an 

 epitome of the present knowledge of 'the Anatomy of the Vegetative Organs of 

 Vascular Plants.' From the very first, the necessity of numerous confirmatory in- 

 vestigations was apparent, since the descriptions at hand were written at very 

 different times, and by very different authors, and it was only possible to judge 

 of and sift the differences necessarily present in these by actual and personal 

 observation. This led to many researches of my own : new results and new 

 questions appeared. The work soon extended itself beyond the limits originally 

 intended. When one section was successfully finished, and others were in hand, new 

 publications appeared which demanded fresh alteration of what had already been done. 

 Therefore, in order that at least something might result, the necessity finally arose 

 of bringing this work of the Danaids, this supplementary patching and correcting, 

 to a definite conclusion, and of finally closing the work. This was done about three 

 years ago. Since then nothing of importance has been done beyond finishing the 

 revision. 



That such was the progress of the work may be some explanation and excuse 

 for the frequent unevenness of the performance. Further, the, so to speak, forced 

 hurry of the conclusion necessarily imposed limits. With regard to the contents, 

 the exclusion in the first place of all Palaeontology and Pathology, the latter 

 including the phenomena of wounding and healing by Callus, &c., is understood. 

 Also the small sections on the throwing off and fall of the Leaf, &c. were omitted 

 as of minor importance. Further, it was unavoidable that the use of the newest 

 Literature should be limited. Much that has appeared in latter years has, to my 

 sorrow, been consciously and intentionally left unused. On the ground of the above 

 explanations, I particularly beg to be excused for this. 



From the older Literature I have perhaps cited too much for many, and for 

 others too little. But here also arose the necessity of keeping a definite limit, in 

 order to bring something to completion. On the anatomy of plants such an 

 indescribable amount has been written, that, in a, comprehensive treatise, one or 

 many authors might be cited in reference to every word. To carry this through, 

 even to the extent to which it is done in the section on Epidermis, makes the 



