1922] 



PAYSON — STUDY OF THELYPODIUM AND ITS IMMEDIATE ALLIES 253 



group — Caulanthus. An exception must be made in the case of 

 Strep tanthella longirostris (Guillenia rostrata of Greene). Al- 

 though probably derived from this group of species, it seems bet- 

 ter to retain it as a separate genus than to transfer it to Caulan- 

 thus. 



It is perhaps most difficult to appreciate the true generic posi- 

 tion of C. lasiophyllus. If it were included in Thelypodium it 

 would have to be associated with T. laciniatum on account of the 

 form of the leaves since it does not resemble, even remotely, any 

 other species, T. laciniatum is one of the most primitive species 

 in the genus. If lasiophyllus were admitted to Thelypodium it 

 would be considered one of the most highly specialized in sev- 

 eral ways. The sessile pods, the corymbose inflorescence, and 

 the numerous trichomes are recent characters. To have a highly 

 specialized species developed from a very primitive one would be 

 somewhat surprising since there would be no known intermedi- 

 ates. The annual habit of lasiophyllus does not accord with the 

 usual biennial habit of Thelypodium. The recurved pedicels are 

 also an aberrant character. From Caulanthus in the old, restricted 

 sense, C. lasiophyllus is equally aberrant. If, however, the genus 

 is enlarged to include C. anceps and C. flavescens, C. lasiophyllus 

 does not seem out of place. Caulanthus flavescens has been 

 known in Caulanthus for many years (as C. procerus) and has 

 not been considered aberrant there. If this is admitted the in- 

 clusion of lasiophyllus is logical. Intermediate between lasio- 

 phyllus and flavescens is C. anceps. The three are evidently 

 related and the differences are slight. C. lasiophyllus has a sep- 

 tum similar to that in Thelypodium but it has evidently been 

 developed independently. 



Stanfordia. — As pointed out elsew T here it is considered best to 

 unite this monotypic genus with that group to which it is very 

 certainly related. The single distinctive character it possesses 

 (the trifid cotyledons) is not thought to be of sufficient import- 

 ance to warrant its generic independence. 



GEOGRAPIirCAL DISTRIBUTION 



Caulanthus is slightly more restricted in its distribution than 

 is Thelypodium. Its species occur in the arid parts of western 

 North America and chiefly between the Mexican boundary and 

 the northern limits of California, Nevada, and Utah. One spe- 

 cies, C. lasiophyllus, is known to occur in peninsular California 



