126 



ProceedhKjs of the Royal Irkh Acadeniij. 



so, are those species of plants which grow solitary amongst the social 

 species, as aycII as those whose existence depends on the conditions 

 determined by the presence of the other plants, such as shade plants, 

 parasites, &c. According to this view, then, the plants composing 

 an association may be classified as {a) Dominant social forms; 

 {h) Secondary social forms struggling for dominance ; {c) Dependent 

 species. 



Por a history of the gradual development of this mode of viewing 

 the vegetation of a district, not as a heterogeneous mass of plant species 

 to be analysed and brought into the compass of a flora, but as con- 

 sisting of a number of associations of living organisms adopted for life 

 under particular conditions of environment, reference should be made 

 to an admirable paper by the late Eobert Smith (1). In this paper, 

 starting with the work of Yon Humboldt in 1805, the progress in the 

 study of " vegetations," rather than that of floras, is traced up to 

 the year 1898, and a copious and most important bibliography is 

 appended. Into this history, and the details of the bibliography given, 

 it is not necessary for us to enter here, but we may content ourselves 

 with singling out for mention one or two of the most important 

 general works which deal with plant- geography from the ecological 

 point of view. 



Foremost among these is Warming's ecological plant-geography (2) 

 which first appeared in Danish in 1895, has since passed into the 

 second of its two editions in German, has been translated into Eussian 

 with additions, figures and a map, but which has, unfortunately, not 

 yet been published in English. This book marks an epoch in the 

 literature of this subject, and is almost indispensable to the student of 

 vegetation. 



Not less important is the admirable text-book of plant geography 

 by the late Prof. A. P. "W. Schimper (3), with its wealth of illustra- 

 tions, published in German in 1898, and in English five years later. 

 In both of the above-named important volumes very full references 

 will be found to the original literature of the subject as it existed 

 up to the dates of their publication. 



Purther, amongst a series of important monographs on the vegeta- 

 tion of the globe, being brought out by Engler and Drude, that of 

 Graebner, dealing with the North-German moors (4), deserves to be 

 specially mentioned, an important summary of which will be found 

 in a paper by Wm. G. Smith (5). In addition to these works, a small 

 botanical guide for North Germany (6) has just recently been brought 

 out by Graebner for use on field excursions, to which attention may 



