Protologue Description: Rubus Janssonii, spec. nov.

Decumbens, validissimus, paene glandulosus inflorescentia; a R. Grimesii differt: foliosior, foliola primocanorum multo latiora; floralia foliola majora, ovata vel oblonga, sensim acuminata; inflorescentia fere racemosior.
To be keyed with R. Grimesii (page 316) but a less glandular and more leafy plant and without the small broad floral leaves shown in Fig. 158, being oblong or narrow-ovate and long-pointed, pedicels scarcely armed, the well-developed clusters more racemose. Strong much-foliaged plant making mounds or tangles 2 or 3 feet deep, with stout primocanes at first erect but later bending over and many of them rooting strongly at tip late in season: primocanes angled at first but becoming terete and very woody, glandless, prickles mostly only 4 or 5 to the inch and weak at first but becoming stout and curved on main axis; leaves of primocanes large, essentially glabrous above but variously soft-pubescent underneath, margins strongly double-serrate. petiole and ribs armed; leaflets 5, ovate to narrowly or oblong-ovate, mostly prominently acuminate, terminal one often 4 inches or more long and more than half as broad with subcordate base (larger and broader than the corresponding tapering or round-based ones of Grimesii) : leaflets 3 in floricane leaves, narrower unless perhaps on strong sterile laterals; foliage on flowering shoots very different between main and secondary slender branches, but all narrow-ovate to oblong and sharp-pointed; axes of floral shoots pubescent but sparsely if at all glandular: flower-clusters terminal on leafy floral axis, bearing 10 or fewer medium-sized flowers on unarmed but mostly lightly glandular short pedicels; calyx only faintly or sparsely glandular to glandless.
Dry open woods near Poquonnock Lake, Groton, New London County, Connecticut, 1931 and 1932, K. P. Jansson no. 105 (type). Dry roadside in large colony, South Hadley, Hampshire County (Connecticut Valley); Massachusetts, L. H. B. A large sterile plant seen by myself in eastern Virginia apparently belongs to this species.