abstracts: botany 97 



PETROLOGY. — The aimlcite basalts of Sardinia. Henry S. Washing- 

 ton. Jour. Geology, 22: 742-753. 1914. 

 At Monte Ferru and elsewhere in Sardinia lavas occur which show 

 in thin section small round isotropic areas, resembhng sections of leu- 

 cite, so that the rocks have been commonly held to be leucite basalts. 

 A careful study and three chemical analyses of these rocks, collected 

 during the author's trip to Sardinia in 1905 for the Carnegie Institution 

 of "Washington, show that the supposed leucite is in reality the hydrous 

 soda mineral analcite, and that it is of primary origin. Comparison 

 with similar rocks from other regions indicates that some so-called leu- 

 citic rocks are in fact analcite-bearing, and that rocks containing pri- 

 mary analcite in well-developed crystals are much more abundant than 

 has been supposed. Analyses are also given of the augite and olivine 

 which form nodules in one of the lavas, the optical study of which is 

 to be taken up later. H. S. W. 



PETROLOGY. — I Basalti Analcitici della Sardegna. Henry S. Wash- 

 ington. Boll. Soc. Geol. Ital., 33: 147-167. 1914. 

 An Italian translation of "The analcite basalts of Sardinia" (J. Geol., 

 22:742-753. 1914); abstracted above. An appendix is added which 

 gives a brief outKne of the quantitative classification of igneous rocks. 



H. S. W. 



BOTANY.^ — Mutation in Egyptian cotton. T. H. Kearney. Journal 

 of Agricultural Research, 2:287-302, pis. 17-25. July, 1914. 



Four varieties of Egyptian cotton, each distinguished by numerous 

 well marked characters, have been developed during the last ten years 

 in Arizona. Two of the new varieties are here described for the first 

 time. Evidence is brought forward to show that these varieties, as 

 well as the numerous varieties of this type of cotton which have been 

 developed in Egypt, have arisen by mutation, their mode of origin pre- 

 senting many analogies to that of mutants of Oenothera Lamarckiana 

 described by DeVries. 



Mutation among higher plants is defined in this paper as "a type 

 of variation manifesting itself in the sudden appearance of a distinctly 

 different individual, the characters of which are uniformly expressed by 

 its descendants when self-pollinated or cross-pollinated only among 

 themselves." 



