Rubus is a remarkable genus in several respects. It has spread to all the continents; it shows signs of decay in its reproductive system whilst it is still in process of evolution, and so offers an opportunity of observing the origin of species. The best approach to a study of the genus is to try to identify the brambles met with, and in the endeavour, knowledge comes. The present work includes descriptions of all the forms found in Great Britain, Ireland and the Channel Isles, three-quarters of which are also found on the Continent.

On account of their relatively slow methods of distribution, their hardiness and the consequent preservation of old forms, the Rubi afford perhaps an unrivalled instrument for ascertaining the movement and succession of florulas and floras, if they are studied in connexion with the climatic and geological changes of the past.

If they may be comparatively unknown to most persons, they are nevertheless no strangers to any of us. From their wild habitats—woods and heaths, mountains and moors—they come to our hedges and garden fences, offering their flowers, like little roses, and then their fruit to our regard, after the cultivated bush fruits are all over. They readily accept the hospitality of a garden, and if taken in hand will be found, some of them, to yield delicious fruit if they are protected from the thrushes and allowed to ripen.

The principal object of the present work is to furnish the means of identifying any native species met with, and the means of understanding the causes and types of variation, and in some measure the probable natural relationships of the species. It has to be remembered, however, that the study of Rubi is still in an early stage of investigation, and there is room for much pioneering work in many directions.

A conspectus of species is prefixed to the descriptive part of the work, analysed to small ultimate groups of species, which are placed in order of frequency within their group. In addition the very common species are distinctively marked, and those other geographically restricted species are also suitably indicated. It is believed that these and other novel aids adopted in the main descriptions will speed identification and serve better than any other scheme.