42 MERRILL! SYSTEMATIC POSITION OF THE "RAIN TREE" 



The main sandstone or typical Nugget. The main sandstone 

 which constitutes the greater part of the formation is typical 

 Nugget sandstone. In many places it consists of brick-red, 

 platy, fine-textured sandstone in beds 1 to 6 inches thick, which 

 form rounded hills that are strewn with angular, platy blocks 

 weathered from the ledges. In other places the sandstone is 

 somewhat firmer, coarser textured, and pinkish to whitish in 

 color. Markings resembling footprints and other impressions 

 were collected from these sandstones, but they proved to be too 

 indistinct for identification. The lighter colored sandstones are 

 somewhat quartzitic and weather into angular blocks that form 

 a dark purplish talus. The top of the sandstone is not exposed, 

 or has not been recognized, for the stratigraphically overlying 

 Twin Creek limestone has been faulted irregularly across the for- 

 mation. The thickness of the main sandstone has not been 

 measured but it is estimated at not less than 1500 feet. 



The thickness of the entire formation appears to be as much as 

 2400 feet in the Fort Hall Indian Reservation and it may be 

 somewhat greater. 



BOTANY. — The systematic position of the "rain tree," Pitheco- 

 lobium Saman. E. D. Merrill, Bureau of Science, Manila, 

 P. I. (Communicated by William R. Maxon.) 



The genus Pithecolobium as interpreted by Bentham is rather 

 a heterogeneous assemblage of plants. Some of the species 

 placed under this name differ so radically from typical represen- 

 tatives of Pithecolobium that in some instances sectional differ- 

 ences within the genus are decidedly greater than the distinctions 

 between some of the universally recognized genera of the Mimo- 

 soideae, while within the section Samanea the same statement 

 holds for specific differences. It is believed that Pithecolobium 

 will be a much more natural group if certain species be removed 

 from it. At the present time, however, I am concerned especially 

 with but a single one, the well known "rain tree," Pithecolobium 

 Saman Benth., a native of tropical America but now extensively 

 planted in most tropical countries. 



Among other species placed in the section Samanea of Pithe- 



