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can teach us many things. It is by no means completely 

 known, but its larger features are clearly perceptible and every 

 new observation fits into the scheme of things and has a signifi- 

 cant meaning. We are at the stage when analysis permits 

 synthesis, and the scientific harvest can be gathered in. 



Perhaps the most indispensable publication on British plants 

 is the London Catalogue, which covers the flowering plants, 

 ferns and their allies, and Charophyta. It enumerates all the 

 species, giving the number of geographical units in which each 

 is found, and indicating which are native, which introduced. 

 The first edition was published in 1844. The one current when 

 I began to study botany was the seventh. It bears no date, 

 but was published in 1874, according to a statement in the 

 eighth edition. My copy refers to the year 1880 in an advertise- 

 ment on the cover, so I suppose it represents a later impression. 

 The eighth edition appeared in 1886, and was reprinted in 1890; 

 I possess the reprint. The ninth edition is dated 1895. The 

 last published, the eleventh, has recently (late in 1925) appeared. 

 It is interesting to note the increase in recorded species of 

 flowering plants: 1601 in the seventh edition, 1760 in the eighth, 

 1861 in the ninth, 2256 in the eleventh. This increase is partly 

 due to "splitting," partly to the discovery of plants hitherto 

 overlooked, partly to the naturalization of aliens. The aliens 

 are less numerous than one might expect; thus it is much easier 

 for European weeds to get established in North America than 

 vice versa. In the eleventh edition the plants which are 

 certainly or most probably aliens include about 267 species, 

 which is after all more than one in ten. These include some 

 of the well established and familiar species, such as Lychnis 

 githago, Centaurea cyanus, etc., which now have the aspect of 

 natives. A very striking feature is the enormous number of 

 hybrids, along with the fact that they are reported only in 

 certain genera. The eleventh edition records the following hy- 

 brids: Ranunculus, 4 (all in Batrachium); Papaver, i; Fumaria, 

 I; Nasturtium, i; Helianthemum, 2; Viola, ii; Polygala, i; 

 Silene, i; Lychnis, i; Cerastium, 3; Sagina, i; Spergularia, 2; 

 Hypericum, i; Geranium, i; (not one in Leguminosae); Prunus, 

 j; Rubus, 23; Geum, i; Potentilla, 3; Rosa, 26; Sorbus, 3; Saxi- 

 fraga, 3; Drosera, i ; Epilobium, 35; Apium, i ; Galium, i; Erigeron, 

 I; Bidens, i; Senecio, 3; Arctium, i; Carduus, i; Cnicus (i. e. 



