114 COLLINS AND KEMPTON: A NEW HYBRID 



stituents, especially the columbates, tantalates and titanates, 

 but also some sulfo-salts (binnite, tetrahedrite), halides (fluo- 

 cerite, yttrocerite), oxides (striiverite, uraninite), silicates (some 

 pyroxenes and amphiboles, to account for the composition of 

 which the conception of isomorphous replacement has to be 

 made unreasonably broad), etc. 



It is customary at the present time to consider this variability 

 as due to " solid solution." Of course, the mere giving a phenome- 

 non a name does not explain it, but whatever may be its signifi- 

 cance its existence cannot be denied and should not be over- 

 looked. Consequently, even crystallinity cannot fairly he regarded 

 as a certain criterion of the absence of ^^ solid solution'^ or accord- 

 ingly of the definite chemical composition of a inineral.^ 



In conclusion, it may be urged that in future text-books and 

 writings dealing with the establishment of mineral species, notice 

 be taken of these relations, and that there be included along 

 with the simple, essential formula of each mineral, in so far as 

 one can be recognized, a statement of the extent to which vari- 

 ations in its composition occur. 



BOTANY. — A hybrid between Tripsacum and Euchlaena. G. N. 

 Collins and J. H. Kempton, Bureau of Plant Industry. - 



In connection with studies in the heredity of maize and re ated 

 plants a fertile hybrid has been secured between Tripsacum dac- 

 tyloides L. and Euchlaena mexicana Schrad. 



Euchlaena mexicana or teosinte is an annual grass, native in 

 Mexico, often grown for forage. The variety grown in the United 

 States requires a long season to mature and the only place where 

 seed is produced is in southern Florida. Tripsacum dactyloides 

 is a perennial grass, native in many parts of eastern United 

 States. The plant is of no economic importance. 



The genera Euchlaena and Tripsacum are placed in separate 

 groups of the tribe Maydeae and the plants are so different that 



^ This is in no way intended as a denial of the definite molecular structure of 

 crystals; and that it is quite possible to reconcile the latter conception with the 

 existence of solid solution will be shown in a later paper. 



' Presented before the Botanical Society of Washington, February 3, 1914, 



