Books and Current Literature. 277 



tion of statistical detennination. The mode of procedure is de- 

 scribed as follows: "A frame whose surface measure is one- 

 tenth of a square meter is thrown at haphazard fifty times, and 

 for each throw all species found within the frame are noted. 

 Thus the dominating species will be noted fifty ti^iies or only a 

 little less, the rare ones only some few times. Different methods 

 and frames of different square measures have been tried. vSmall 

 frames and many throws give more correct numbers than larger 

 frames, this being controlled by short counting, but for practical 

 use the author finds fifty throws of a frame one-tenth of a sqtiare 

 meter sufficient." By this means the dominant species of a given 

 formation as well as those of subordinate rank, are clearly indi- 

 cated with practically complete elimination of the personal 

 element. 



The action of the legislature of Michigan ia 190.5, in re- 

 quiring the State Geological Survey to extend its scope so as to 

 include a biological survey of the state has been amply justified 

 during the few years the law has been efl'cctive, and conspicu- 

 ously so in the case of the recently published Report o/i the Geology 

 of Tuscola County, Michigan, bv Charles A. Davis. The eighth 

 chapter of this report is devoted to the native vegetation of 

 Tuscola County, w^iich, from its position in the "thumb" of 

 Michigan, with Saginaw Bay on the west and Lake Huron on the 

 east, and the peculiariteis of its recent geological history, pre- 

 sents an ensemble of environmental conditions which render of 

 special interest the author's study of plant distribution in the 

 area under consideration. 



Discussing the influence of climatic factors. Dr. Davis shows 

 that the temperature effects of Saginaw Bay, though less than 

 those observed in the part of the state lying near Lake Michigan, 

 are such as to be distinctly felt, and are apparently the cause of 

 the occurrence of the "prairie" flora of the area immediately 

 adjacent to the marshes of Saginaw Bay, far to the north of any 

 similar group of plants known to exist in that region. Some of 

 these plants are more than a hundred miles north of the nearest 

 outside stations known for thnn. 



