This is an interesting and valuable assemblance of varieties which has been classed as a true species, Rubus neglectus. It appears to be intermediate in character between the black caps and the American red species. Fuller says of it: "The principal difference between the varieties of the black caps and purple cane is in the fruit. The first, as is well known, has a rather dry, tough fruit with a peculiar flavor. Its grains are numerous and very irregular in size. The fruit of purple cane, as a rule, is rather soft, juicy, often very brittle, the grains separating very readily; color varying from light red to dark brownish purple, but never black; the flavor mild and agreeable, but entirely distinct from those of the true black-cap raspberry."
Professor Bailey says of the purple-cane family: "The type has no characters which are not found in one or both of the other two. Neither has it any normal or continuous range, but occurs where the black and red species are associated. All this points strongly to hybridity; and there is now sufficient accumulation of experimental evidence to prove a hybrid origin for these berries."
As the botanic classification is uncertain, and the close relation to the black caps is evident, it is usual with growers to class the purple-cane varieties that root from the tip of the canes and never sprout from the roots with the black caps (242. The Black-cap Family (Rubus occidentalis)). This leaves a small but excellent class which, like the Philadelphia, are not easy to root from the tips of growth and not sprouting as freely as the red varieties.