INTRODUCTION. 



OF the two branches of the Organic World, the Vegetable Kingdom 

 might be expected to present a simpler problem of Descent than the 

 Animal Kingdom, on account of the prevalent non-motility of the mature 

 individual. That fixity of position which the Higher Plants show, should 

 tend to a more obvious record of previous events than the ambulatory 

 habit of Animals, and especially of their higher types, would seem to 

 allow. It is reasonable to expect that organisms of fixed position 

 should demonstrate in their distribution some traces of their past history ; 

 these would be specially valuable in the elucidation of the problem of 

 the Origin of a Land Flora, and of the relation of the Land-growing 

 Plants to those of the water. 



But this prima facie probability is largely discounted by the extra- 

 ordinary facility shown by Plants for the distribution of their germs. A 

 comparison of the Higher Animals with the Higher Plants in respect 

 of motility shows that the motile parent in the former is without special 

 provision for distribution of its germs, while the Plant with its fixity of 

 station shows high elaboration and variety in the methods of their 

 dissemination. In consequence of this there will be a natural tendency 

 in the vegetable kingdom, as there is also in that of animals, towards 

 the obliteration of any such genetic record as the fixity of position of 

 the individual plant during its active vegetation might otherwise have 

 been expected to have left. Accordingly, on examination of the vegetation 

 of any ordinary country-side, its uplands and lower levels, its swamps, 

 streams, and pools, plants of the most varied affinity are found to be 

 promiscuously shuffled together, and show little sign of ranking in their 

 position according to their descent. For instance, the Flora of still 

 fresh waters may be found to consist of such plants as various green 

 Algae and Characeae ; of Isoetex and Pilularia ; together with Angiosperms, 

 such as Littorella, Lobelia, and Subularia. In flowing mountain streams, 

 in addition to green Algae may be found Chanlransia and Lcmanea, 

 associated with Fontinalis and sundry Angiosperms. Conversely, in various 

 positions on land, along with certain Algae in moist spots, representatives 



