168 



SCIENCE. 



[N. S. Vol. XIX. No. 474. 



Crawford Counties, Michigan. The soils 

 are classed as clay, clay loam, sandy loam, 

 and sand, power to hold and lift water 

 from an underground water level decreas- 

 ing with the different soils in the order 

 named. The region is glacial and consists 

 of ridges and plains. The former are usu- 

 ally gravelly and sandy loam. The latter 

 are loamy sand, clay or nearly pure sand. 

 Some ridges are quite clayey. The vegeta- 

 tion is divided into (I.) upland and (II.) 

 lowland types. Of the former are consid- 

 ered the following, named for the charac- 

 teristic tree species: (1) The hardwood, 

 (2) the white pine, (3) the Norway pine 

 and (4) the jack pine. These types be- 

 come more xerophytie in character in the 

 order named. In general, the upland 

 types follow in their distribution the dis- 

 tribution of the soils, the hardwood occur- 

 ring on low clay plains, on swamp margins 

 in loamy soil, and on certain plains of loam 

 which are well covered with humus. The 

 white pine occurs on certain ridges of clay 

 loam and of clay and also on swamp mar- 

 gins in loam and clay. The Norway pine 

 type is found on loamy sand plains and 

 on the ridges of sandy and gravelly loam. 

 The jack pine type occupies exclusively 

 the well-washed sand plains. The only 

 complicating factors in distribution are 

 the effect of humus (which seems able to 

 make even sand able to support hardwood) 

 and the effect of the rise of the under- 

 ground water level, as at swamp margins. 

 The latter makes a sandy soil able to bear 

 vegetation which would otherwise be 

 found only in loam or clay. Analyses of 

 the soil seem to show that its chemical 

 properties are unimportant, that the real 

 factor to determine distribution is the 

 power of the soil to hold water, this power 

 increasing with fineness of pai-ticles or 

 with presence of humus. 



Research Methods in Phytogeography : F. 



E. CijEments. 



(1) The use of simple and automatic 

 instriunents, photometer, psychrometer, 

 thermometer, etc., in the exact determina- 

 tion of the physical factors of a habitat; 

 (2) the study of the structure and devel- 

 opment of formations by means of perma- 

 nent and denuded quadrats, and migration 

 circles; (3) experimental ecology in the 

 field by moving plants from one habitat to 

 another, or by modifying the controlling 

 factor of a habitat; (4) experimental ecol- 

 ogy in the plant house by equalization and 

 control of physical factors. 



Ensayo para la formacion de un foto-heri- 

 ario Botanico y medico de la flora Mexi- 

 cana: Fernando Altamirano.* 

 Contendra una coUeccion de 6000 foto- 

 grafias tomadas de los especimenes del 

 Herbario de Plantas Mexicanas del Insti- 

 tute Medico Nacional. Cada fotografia 

 sera de y llevara dos etiquetas: una corre- 

 spondera al Coleetor y tendra los datos de 

 clasificacion, lugar de vegetacion, etc., y la 

 otra correspondera al institute, conten- 

 iendo los nombres vulgares, las rectifica- 

 ciones que se hayan hecho a la clasifica- 

 cion, etc. Cada lamina del Foto-herbario, 

 que contendra 4 foto-grafias, ira accom- 

 panada de una hoja de igual temaiio (0.20 

 per 0.25 proximamente), conteniendo 

 datos descriptivos, aplicaeiones y la distri- 

 bucion geografiea con su mapa respective. 

 Las plantas del Herbario seran fotografia- 

 das en orden de familias naturales, comen- 

 zando por las Eanunculaceas. Cada lam- 

 ina contendra solamente especies de un 

 mismo genero, especies que iran numera- 

 das progresivamente, tal como se repre- 

 senta en la muestra que se remite, la cual 

 comprende 100 fotografias. La impresion 

 del texto y el tiro de las laminas, lo hara 



"■' La palabra foto-herbario sera substituida por 

 otra si se eonsiderare inadecuada. 



