OF ARTS AND SCIENCES: NOVEMBER 11, 1863. 189 



j}hyta, upon flat-podded species of what would otherwise belong to 

 Phaca, the single species of the latter and some species of the former 

 being quite peculiar in habit. But intermediate forms connect the 

 compressed with the turgid and inflated legumes. 



Used for sectional groups, these minor carpological characters may- 

 be turned to good practical account ; for it is no great objection to 

 such natural groups, as it is to genera, that they blend through grada- 

 tions or have occasional exceptions. 



It is in the botany of this country that the question of the distinction 

 between Phaca and Astragalus is most pressing, and where the data 

 for the answer are most largely to be found. While extra-tropical 

 Asia is the focus of true Astragalus, that of Phaca is in America, 

 mainly in North America, with an extension along the Andes into 

 South America. While the Floi-a of the Russian Empire enumerates 

 168 species of Astragalus (of which I suppose more than nine tenths 

 are bilocellate or nearly so), and only six species of Phaca, I recog- 

 nize in the following paper 66 species of the Phaca series to 52 of 

 Astragalus proper. Moreover, rather less than half of the latter are 

 completely bilocellate by a dorsal septum, and at least half a dozen, of 

 different groups, have been or might be referred to Phaca. A. abori- 

 ginum, A. RoUnsii, k.c. are retained in the Astragalus series, on ac- 

 count of the vanishing rudiment of a dorsal septum ; and A. lotiflorus 

 chiefly, and A. microlobus entirely, because of their close affinity to 

 cognate Astragaline species ; while, on the other hand, A. Gooperi and 

 A. Bechwithii, associated with their natural allies among the Phacce, 

 might technically be about as well placed in the other series. 



I cannot avoid the conclusion that Phaca must be merged in Astraga- 

 lus. Also, — since in perhaps the majority of the Phacce there is no 

 intrusion nor peculiar tumidity of the seminiferous suture, — that the 

 subtribe Astragalece of De Candolle has no valid foundation, so that 

 Astragalus is merely a genus of the Galegece. 



The combination of Phaca with Astragalus at once leads us to con- 

 sider the case of Oxytropis. This is a genus founded by De Candolle 

 upon Linntean species of Astragalus, and now pretty numerous in spe- 

 cies. It is characterized by having, along with the legume of Phaca, 

 carried sometimes to an extreme (that is, with the ventral suture 

 septiferous), a beak-like acumination or cusp at the apex of the carina 

 of the corolla, — whence the generic name. Thus Oxytropis, strictly 

 considered, would now appear to rest upon this cusp or tip alone. 



