Page:Transactions of the Natural History Society of Northumberland, Durham, and Newcastle-upon-Tyne 1838 Vol.2.djvu/150

140 Mr. Winch's Observations on his Flora. is another class of Botanists more injurious than these, they too are generally men who set their faces against any increase of genera, but who, at the same time, consider that the most trifling difference in a leaf, a serrature, or a hair, should constitute a specific distinction : and to such an extravagant pitch is this system now carried in certain genera — take Rosa, Rubus, Salix, Myosotis, no two persons are or can be agreed on what constitutes a species and what not, in such tribes. The consequence is, that all sober-minded Botanists will have nothing to do with these genera, and the crazy ones have each their own ideas as to species. You and I may set our faces against these species-mongers, but it is to no purpose."

But as the native Roses, with which this district abounds in a remarkable degree, contribute greatly to the beauty of our woodland scenery and hedge-rows, it may be worth while to inquire into the cause of the difficulty which attends the defining the species of such conspicuous flowers. That there is difficulty in the task we may be assured of, for W OODS, an indefatigable Botanist, in his paper published by the Linnaean Society, in the 12th vol. of their Transactions, enumerates no less than twenty British species, while L INDLEY , who bestowed no less pains on the same subject, in his Rosarum Monographia reduced their numbers to twelve. The difference of opinion, existing between these acute Botanists, must be accounted for by those marks which generally afford permanent specific distinctions in other plants, such as the roughness or smoothness of their leaves, the form of the prickles, whether the segments of the calyx be simple or divided, or the leaves be singly or doubly serrated being of small avail in this genus. To these must be added, the almost insurmountable difficulty that the various species or varieties pass by insensible degrees into each other, and though at first sight, no two Roses may appear more dissimilar than Rosa canina on the one hand, and Rosa villosa on the other, yet links can easily be furnished to form a complete chain between them. Rosa canina is well known as a robust growing bush, with hooked prickles, smooth oval fruit and shining leaves. In Rosa sarmentacea the plant becomes slender in habit, and with us its leaves generally assume a glaucous hue. Rosa Forsteri