18 MINNESOTA STUDIES IN PLANT SCIENCE 



marked with conspicuous longitudinal ridges, each surmounted by an undu- 

 lating septate keel or edge. Hairs uniseriate. Fruit a capsule (Plates I, V). 



Monotypic, including the species described below. 



On a preceding page a reference was made to the distinctions on which 

 Haworth founded the genus Aulaxis — namely on the ground that the 

 capsules are divided almost into two. He also described the capsules as 

 united only at the base "capsulae superae alte bipartitae bast solum coalitae." 

 In this respect his description was accurate. He was mistaken, however, in 

 describing the corolla as irregular '"corolla irregularis." To these distinc- 

 tions he added an accurate description of the seeds. 



Haworth included in the genus a new species, Aulaxis {Saxifraga) 

 nuda which he had separated from Aulaxis {Saxifraga micranthidifolia), on 

 the ground of its glabrous character, but he seems to have left no account 

 of its origin. Seringe (26) embodied the species in the section Hydatica, 

 preceding it with a question mark. In the account of an excursion to the 

 mountains of North Carolina Dr. Gray (9) writes as follows concerning 

 this species: "Aulaxis nuda (Haworth, I.e., of unknown origin) appears to 

 be the more ordinary and more glabrous form of this species" (S. micran- 

 thidifolia Haw.). The species was not included by Torrey and Gray 

 (31) in the Flora of North America. 



The carpels, the mature fruit, and the gland are very distinctive here. 

 In addition the hypog}'ny is complete. At maturity the upper free portions 

 of the carpels spread widely in a V-shaped fashion. No traces of the gland 

 could be detected in the mature stage. The young carpels are quite sharply 

 conical, the beaks soon elongating and terminating in small stigmas. The 

 gland is at first fleshy and envelopes the carpels to the middle. 



The distribution is limited to the Appalachian Mountains, from northern 

 New Jersey to northeastern Georgia. The altitudinal range ascends to 2,000 

 feet or more. 



Saxifraga micranthidifolia (Haw.) Britten, in Britten and Brown, 

 111. FI. 2:174. 1897. 



Robertsonia micranthidifolia (Haw.), Syn. PI. Succ. 322. 1812. 

 Aulaxis micranthifolia (Haw.), Saxifr. Enum. 47. 1821. 

 Saxifraga erosa Pursh, Fl. Am. Sept. 311. 1814. 

 Saxifraga micranthifolia Steud., Nom. Bet. 736. 1821. 

 Saxifraga Wolleana Terrey and Gray, Fl. N. Am. 1 :569. 1840. 

 Micranthes micranthidifolia (Haw.), Small, Fl. S.E.U.S. 501. 1903. 



The species has often been confused with S. pennsylvanica which it 

 somewhat resembles in vegetative characters, but the plants can be readily 

 distinguished by the carpels. There does not appear to be any close affinity 

 between the two (Plate V). 



