280 University of California Publications in Botany. [ VOL - 3 



fairly constant character for separating the two varieties. So 

 far as noted it does not vary beyond reasonable limits, so that 

 there is never any question as to the variety to which any par- 

 ticular specimen belongs. But in all other characters habit, size. 

 pubescence, involucre, etc., the two varieties exhibit the same 

 forms, and since they both run into strictly parallel strains as 

 regards their achenes they cannot be considered as distinct 

 species. 



A splendid series of several hundred specimens of var. Cali- 

 fornicum, recently gathered near San Luis Obispo by Mr. Benj. 

 Cobb, indicates that the achenial characters, although remarkable 

 in their extremes, are of comparatively trivial importance. The 

 central achenes are mostly traversed by straight ribs, or costae 

 In the marginal achenes these ribs vary from slightly undulate 

 to strongly and closely crinkled, so that the surface of the achene 

 appears as though honey-combed (f. crcnulatum). On other 

 plants, gathered at the same station, the marginal achenes vary 

 from slightly swollen and spindle-shaped, with the costae still 

 evident, to strongly swollen and balloon-like, all traces of costae 

 01 ribs having been obliterated through the stretching of the 

 surface (f. turgidum). The same variation, but to a more lim- 

 ited extent, is observable in collections from other localities. 



120. CREPIS L. 



Herbaceous annuals, biennials, and perennials, similar to Hie- 

 racium but distinguished from that genus by the shape of the 

 achenes and by the pappus. Involucre cylindric or campanulate ; 

 its principal bracts in a single row, equal, with more or less thick- 

 ened midribs ; the outer calyculate ones much smaller or wanting. 

 Flowers yellow. Achenes narrowed toward the summit and 

 sometimes also at base, 10 to 30-ribbed. Pappus copious, white 

 and soft. 

 Introduced species: root annual or biennial. 



Involucre 7 to 9 mm. high : achenes 10-striate 1. C. virens. 



Involucre 9 to 12 mm. high : achenes 13-striate 2. C. biennis. 



Native species: root perenniaL 



Involucre 5 to 10-flowered, its principal bracts only 5 to 8 



3. C. acuminata. 



Involucre 10 to 30-flowered, its principal bracts 8 to 24 



...A. C. occidentalis. 



