].3a 



a "head," while in the former it was elongated and the spikelets 

 somewhat separated. I had found that the keys when marie to 

 work conc;lusively at all (commonly with both, or all, divisions 

 used and the elimination method necessary) generally threw 

 together plants which certainly did not form a thoroughly con- 

 sistent series. Several years ago a student of Carex at whom I 

 thrust our accumulation of puzzling Muhlenhcrf^ianae in the 

 Herbarium of the Philadelphia Botanical Club, in endeavoring 

 to associate the specimens with species known to him, w^as com- 

 pelled, on my pressing him for opinions, to throw together plants 

 which on examination showed in series a very palpable lack of 

 homogeneity. 



Under such circumstances the general botanist, everywhere, 

 apparently, rather gives up in despair of naming such plants 

 and waits for a more convenient season to work upon them or 

 the coming of the specialist. 



It was no small satisfaction to see Mr. Mackenzie take up this 

 matter and find several well-marked new species in the Miihlen- 

 hergianae. When the opportunity arose to assist Mr. Mackenzie 

 in gathering data on the regional distribution of various of our 

 less well-known Carices in his work upon the Carex portion of 

 Mr. Norman Taylor's Flora of the Vicinity of New York, a 

 number of these puzzling Aluhlenbergianae were brought forward 

 with high hopes of an ultimate and satisfactory solution of their 

 identity. 



Some of these were only Muhlenbergii, a few cephaloidea, but 

 several proved to be the little-known austral species Carex 

 aggregata, which Mr. Mackenzie wrote me were the first specimens 

 he had seen from north of Washington, D. C. W^ith this authen- 

 tically determined material and the original key* for this group 

 in the new Illustrated Flora it was soon found that, especially in 

 the Muhlenhergianae plant so long familiar to me, we had evidence 

 of quite a well-distributed occurrence of this species through 

 southeastern Pennsylvania, extending from the valley of the 



* The absence of bracts in cephaloidea (in contrast to their presence in aggregata) 

 proves to be a weak character and one unsatisfactory for use in a ke}-. The key- 

 in Taj-lor's Flora has been much improved over that in the new edition of the 

 Illustrated Flora. The sheath and the scale characters are very distinctive. 



