182 PROCEEDINGS OF THE AMERICAN ACADEMY 



The nebula H. IV. 33, in the position 1830.0 5^^ 28-" 7^ 8—6° 51', 

 described by W. Herschel as " a star with a milky chevelure or v. B. 

 nucleus with milky nebulosity," appears in the Great Refractor as a fine 

 annular nebula or cluster, very much concentrated on the following side 

 almost to a stellar centre. 



Professor Cooke gave a description of a new and improved 

 Spectroscope made by Mr. Alvan Clarke. It has nine prisms 

 of plane glass sides filled with bisulphide of carbon, which are 

 so mounted and arranged that they are capable of easy adjust- 

 ment to the angles of least deviation in the refracted ray. By 

 this instrument Professor Cooke has been able to discover a 

 much greater number of lines in the solar spectrum and in 

 metallic spectra than have hitherto been observed. 



Dr. Gray presented the two following papers : — 



On Streptanthus, Nutt., and the Plants which have been re- 

 ferred to that Genus. By Asa Gray. 



A number of plants have been referred to Streptanthus, — some by 

 its founder, Nuttall, and others by myself, — which, upon re-examina- 

 tion, appear to belong elsewhere. Having now before me all the au- 

 thentic materials which exist in herbaria in this country, I have endeav- 

 ored to clear up the group, with the following results. 



1. STREPTANTHUS, Nutt. 



The characters of this genus are the linear or elongated and sagit- 

 tate anthers, and petals with long canaliculate claws (with or without 

 a dilated lamina), along with the flattened siliques and broad flat 

 seeds of Arabis. lodanthus, Torr. & Gray, and Thelypodiurn, Endl. 

 {Pachypodhim, Nutt.), which have long unguiculate petals and narrow 

 anthers (which coil or curve when effete, like those of Streptanthus), 

 have terete and torulose siliques, the valves with an obscure if any 

 mid-nerve, and oblong seeds, the cotyledons in the latter obliquely more 

 or less incumbent. There are transitions which connect, quite too 

 closely, Streptanthus with Arabis. But the genuine species of the 

 former are so strikingly marked, that the genus will pi'obably be kept 

 up. The disposition of the calyx to assume a crimson or purple color, 

 and of the filaments of the longer stamens to unite in pairs, may also be 

 taken into account. I recognize the following species. 



