540 Rydberg : Notes on Rosaceae 



is a form of 5. latifolia, growing in rocky places, especially along 

 streams, with short broad leaves, rounded at the apex and coarsely 

 toothed. It is also much lower than the ordinary 5. latifolia, and 

 the stems usually die back each year to near the base. This was 

 described as ^. obovata by Rafinesque. Usually it is very unlike 

 the ordinary 5. latifolia, but intermediate forms are not infre- 

 quent. This form needs more field study. 



In the North America Flora, there are five new species pro- 

 posed. These, together with S. pyrainidata, the author is inclined 

 to regard as hybrids, except S. Helleri. Hybrids are not uncom- 

 mon in the genus Spiraea. S. Nobleana was described by J. D, 

 Hooker from a plant raised in a California nursery. It is supposed 

 to be a hybrid between 5. Doiiglasii and 5. salicifolia. As one 

 of the supposed parents is a native of North America and the other 

 is occasionally found spontaneously, and as the plant originated 

 in America apparently without the help of man, it might have been 

 included in the North American Flora, but it was excluded there- 

 from, like all other garden plants. The native species of probable 

 hybrid origin and their probable parents are as follows : 



S. roseata = S. Menziesii x densiflora. 



S. subvillosa = 5. Doiiglasii x. densiflora. 



S. tomentidosa = S. Douglasii x lucida. 



S. pyramidata = S. Menziesii x lucida. 



S. subcanescejis = 5. tomeniosa x alba. 



Spiraea tomentulosa, and ^. snbcanescens are known only from 

 the type locality. 5. s2ibvillosa has been collected also at the 

 following station : 



Oregon: Hood River, Cascade Mountains, Aug. i, 1894, F. 



E. Lloyd. 



S. roseata has been collected at the following locality : 

 Idaho : Near Cooper's, July 20, 1892, Isabel Midford. 



Petrophytum and Kelseya 



It is gratifying to the author, that C. K. Schneider,* a rather 



conservative dendrologist, has independently raised these to generic 



rank. The genera are related to Spiraea, but are distinguished 



by the peculiar habit and by the stru cture of their fruits. To 



* Handb. Laubh. i : 484, 485- I905- 



