94 New Genera and Species of 6p. 



broad silicjue, margined, and even winged seedst) is consider- 

 able, but it differs widely in the shape and color of the petals, 

 the structure of the dissepiment, and in many other respects. In 

 the broad silique and dissepiment (compared with any of the 

 Arabideae) it seems allied to some Alyssineae, especially if we 

 retain in that tribe the remarkable Selenia of Nuttall, which re- 

 sembles our plant in the transverse areolae of the dissepiment, 

 pinnatifid leaves, and yellow flowers. In that genus, how- 

 ever, the fruit is broader, the style longer, and the seeds are 

 truly accumbent, although the radicle is unusually short, 

 and is directed horizontally with respect to the axis of the fruit. 

 Upon the whole I consider it more nearly related to Selenia 

 than to any other known genus. 



Description of the Plate of Leavetiworthia. 



Fig. 1. A young plant of L. aurea, of the natural size. 



2. A full grown plant of the same. 



3. A flower magnified. 



4. A petal do. 



5. The silique laid open to show the arrangement of 



the seeds. 



6. The replum and dissepiment, exhibiting the longitu- 



dinal nerve, and the funiculi. 



7. The embryo. 



8. A transverse section of the same. 



9. Pistil of L. Michauxii. 



10. Silique of the same. 



11. Embryo. 



