746 



8CIENCK 



[N. S. Vol. XI. No. 280. 



though, as in the other strata of the State, the 

 preservation of the fossils leaves much to be de- 

 sired. It is to be regretted that the absurd pale 

 yellows allotted by international agreement to 

 the Tertiary, make it almost impossible to pre- 

 pare an intelligible map of a Tertiary region in 

 color. We should advise Professor Harris in 

 future to use plain black and white symbols for 

 this purpose. 



The work on the Tertiary accomplished by 

 this survey is most important, and would have 

 been impossible for any one less versed in the 

 lower Eocene paleontology than Professor 

 Harris. He demonstrates the presence of the 

 Midway horizon in Louisiana, for the first time, 

 in two localities and further search will doubt- 

 less reveal others. 



The Chickasawan (Mansfield of Hilgard's 

 earlier work and one of the multitudinous 

 ' Lignitics ' of authors) is now found to cover 

 a large area in Louisiana. Parts of it, through 

 absence of expert paleontological knowledge, 

 have been referred to the Vicksburg, Jackson, 

 Claiborne and other subdivisions of the Eocene, 

 in earlier work. Now we have its boundaries 

 approximately defined and a well illustrated 

 faunal list of species provided. In future work 

 we trust Professor Harris will discard entirely 

 the obsolete and misleading name of Lignitic 

 and adopt the geographical term for this stage 

 which is accepted by the majority of geologists 

 interested in this horizon. 



Jacksonian strata extend, as the author 

 shows, from the Oachita river to the Texas 

 boundary, while the Oligocene beds of the 

 Vicksburg horizon are confined to the region 

 between the Oachita and Red rivers. 



Considering the small appropriation available 

 for the work, the State of Louisiana is to be 

 congratulated on the amount and quality of 

 that which has been accomplished. It is to be 

 hoped that Professor Harris may be able to con- 

 tinue his labors, and that the perplexities pre- 

 sented by the Pleistocene deposits of the State 

 may yield to persistent study in the future. 

 W. H. Ball. 



The Physiological Role of Mineral Nutrients. By 

 De. Oscae Loew. Bull. 18, U. S. Dept. of 

 Agriculture. 1899. 



Dr. Loew discusses the actual part of the 

 various mineral substances in the physiology of 

 the vegetable organism, a matter of prime im- 

 portance to the agricultural experimenter, as 

 well as the botanist. Every advance in this 

 subject has been won by the most arduous labor, 

 and only in a few instances may the conclusions 

 reached be considered as final. 



The treatment of such an unsettled subject 

 within the limits of a bulletin must result in 

 many omissions in order to bring points of the 

 greatest interest prominently to the attention. 

 By reason of such necessity one does not find the 

 names of Wieglieb, Marcgraf, Senebiei-, or Bous- 

 singault in the historical resume of the subject, 

 which otherwise traces the course of investiga- 

 tion on the subject somewhat clearly. 



Phosphoric acid is necessary for the formation 

 of the essential constituents of the nucleus and 

 plastids, inclusive of the chloroplasts and chlor- 

 ophyll ; secondary potassium phosphates are 

 found in combination with certain proteins ; 

 iron takes part in the formation of chlorophyll 

 although it does not enter into the composition 

 of the molecule of this substance, and is not to 

 be considered of more importance in this con- 

 nection than many other substances. Attempts 

 to replace iron with manganese have met failure 

 so far. Chorides are necessary for but few spe- 

 cies ; they are taken up in quantity by aquatics 

 and other plants however. 



The presence of potassium salts seems neces- 

 sary for the synthesis and translocation of car- 

 bohydrates and proteins. This element may be 

 replaced by rubidium or caesium in certain 

 fungi. 



The relation of calcium salts to the translo- 

 cation of carbohydrates is not clearly defined, 

 but this suKstance is abundant in all parts of 

 the bodies of the higher forms of plants. It 

 is notable that many of the simpler organ- 

 isms may exist and attain full development 

 without this element, and Dr. Loew advances 

 the theory that the development of the higher 

 plants both in form and diflferentiation of func- 

 tion becomes possible only when the capacity to 

 assimilate calcium and use the resulting cal- 

 cium proteid compounds is acquired ; a theory 

 which is based chiefly on coincidence. 



Magnesium is found in nuclear substances 



