116 WOODY PLANTS 



alternate, torn and irregularly shriveled on the persistent base 

 of the petiole; bundle-trace not discernible; stipules often per- 

 sistent at the top of the petiole remnant. 



Like Crataegus, this is a most difficult group taxonomically. 

 It is believed that the few, ancient, stable species inliabiting east- 

 ern North America at the time of its settlement have given rise 

 through crossing to numerous incipient "species", some fertile 

 and some apomictic, many of which are spreading rapidly. An 

 astonishing number of such "species" seem to appear in certain 

 small areas, for example, in New England, and in the AUeghenies 

 of West Virginia. It is impossible to describe a genus such as 

 this except in a tentative manner, and it will be recognized that 

 identification in winter is virtually impossible. Except for a few 

 clear-cut species of raspberries, the following key is designed to 

 separate the larger groups (subgenera, or sections) only. 



a. Plant habitually unarmed 1. R. odoratus 



a. Plants habitually armed, but 

 with thornless or nearly thorn- 

 less mutations ^ 



b. Canes upright 



c. Canes habitually weakly armed 

 (Raspberries) 



d. Plant red -hairy all over 2. R. phoenicolasius 



d. Plants not red-Lairy 



e. Stems bristly, not glau- j 



cous 3. R. strigosus r 



e. Stems prickly, very 



glaucous 4. R. occidentalis 



c. Canes habitually strongly armed 

 (sometimes nearly thornless) 



d. Canes hispid or setose, prickles 



few (Bristleberries: R. 



setosus Bigel . , etc . ) 

 d. Canes not hispid or setose, 



prickles usually numerous 



(Blackberries) 



e. Canes nearly without prickles 

 or with only a few straight 

 ones (Smooth Blackberries; 

 R. canadensis L. , etc. ) 



