abstracts: botany 295 



all the centers of eruption it is believed that nearly all the varieties 

 described and perhaps some others occur on each of the principal islands. 

 Nephelite-melilite basalts are known on three islands — Kauai, Oahu, 

 and Maui. Strongly feldspathic andesites occur on Hawaii; and the 

 lavas of Kilauea, the youngest volcano of the islands, are predominantly 

 olivine-poor basalts. 



The relations of the magmas as differentiation products are compared 

 with those of other island groups of the Pacific Ocean, and the distri- 

 bution of the Hawaiian types in other parts of the world is considered. 

 Their chemical characters and the circumstances of their association 

 demonstrate that the so-called alkalic and calcic magmas may and do 

 occur together as derivatives from a common source. The current 

 generalization that this distinction between alkalic and calcic series 

 ("Atlantic and Pacific branches") of igneous rocks is of fundamental 

 importance in pedogenesis and may serve as a factor in a natural 

 system of classification is held to be fallacious and to lead to endless 

 confusion. 



The series of Hawaiian lavas are concluded to have been derived 

 from a general magma of nearly the same character in all parts of the 

 province. It does not seem probable that there has been any note- 

 worthy differentiation in the main reservoir beneath the Hawaiian 

 district. During the active growth of each volcano the lavas presented 

 a moderate variability in composition, but definite system in this 

 variation was not detected. With decreasing eruptive activity and 

 possibly attendant contraction and limitation of lava chambers a 

 higher degree of differentiation was accomplished and is shown by more 

 salic and correspondingly more femic lavas than those of earlier date. 

 In the long period of parasitic or subsidiary eruptions conditions were 

 favorable to extensive differentiation. The processes of differentiation 

 are still problems for investigation. Movement under gravity of 

 crystal particles may have played a part. J. Fred. Hunter. 



BOTANY. — On the characters and relationships of the genus Monopteryx 

 Spruce. Henry Pittier. Bulletin of the Torrey Botanical 

 Club, 42: 623-627. 1915. 

 The genus Monopteryx (Fabaceae) was based upon flowering speci- 

 mens of a tree collected by Spruce on the upper Rio Negro, Brazil. 

 Because of the fact that the fruits were unknown, the genus has been 

 erroneously placed among the Sophoreae. Complete specimens of 

 a new Venezuelan species, Monopteryx jahnii, show that the genus is 

 closely related to Pterocarpus. H. P. 



