52 



ECOLOGICAL RELATIONS OF THE FLORA. 



Quadrats. 



Each plant had about 200 sq. cm., assuming even spacing. 



From inspection of the flora hsts it seems that the jack pine barrens 

 are much ahke throughout ]\Iichigan and INIinnesota. Sand Point has 

 80 per cent of Smith's hst of plants tj^pical of the jack pine plains and 

 79 per cent of his list of less frequent plants. Considering the sand 

 region as a whole all the plants in both lists appear. (Smith, 1880, 

 quoted in Beal, 1904, p. 16-17.) 



The most applicable work on the pine barrens is that of Livingston 

 in Roscommon and Crawford counties where the formation is the same 

 as on Sand Point and the relation of the trees to the substratum is 

 similar. From his studies in these places, Livingston draws the con- 

 clusion that the chief factor in determining the distribution of the 

 species of pine is the amount of humus in the soil. (Livingston, 1903, 

 p. 30.) He proves by laboratory" experiments that the relation of this 

 constituent to the amount of water in the soil is an important one by 

 demonstrating that humus soil holds nearly twice as much water as 

 sandy soil. He considers the mineral elements in the soil sufficient 

 for plant growth, but the analyses given by Kedzie (1888 and 1893) 

 seem to show that these mineral constituents, especially the salts of 

 Potassium, Phosphorus and Nitrogen, are insufficient.* Furthermore 

 these salts are not made available because of the lack of organic acids 

 in the soil water and the analyses of soil water from West Olive, 

 Michigan, as furnished by the Michigan College of Agriculture, show 



* See footnote opposite page. 



