1918] ; CURRENT LITERATURE 391 
depressions, and the other that following fire. In connection with the former, 
he distinguishes the usually recognized types of marsh and bog vegetation and 
states that the main distinction between the two is in the rate of growth, the 
slow rate of growth in bog plants being largely explained upon the basis of a 
dearth of mineral plant food in the substratum, which is also supposed to 
account for the presence of the same species upon the uplands in colder climates. 
o experimental evidence is given in support of this explanation. It is also 
rather surprising to be told that bog vegetation is ‘“‘sometimes erroneously 
called xerophytic,” after the almost endless discussion of bog xerophytes. 
eficiency of mineral plant food is also given as an explanation of the 
slow progress toward mesophytism of the pine forests upon sandy uplands. 
Leaching is supposed to prevent the accumulation of any considerable amount 
of plant food near the surface of the ground. This may possibly hold for the 
sandy plains, but if so it is difficult to see why it should not also apply to the 
pure sand of the dunes, where mesophytic forests develop rather quickly and 
where the conifers are soon largely replaced by deciduous species 
In discussing the influence of fire upon forest establishment, the error is 
made of stating that the cones of Pinus Banksiana remain closed and attached 
to the tree for many years, opening and discharging their seed after burning. 
Closer observation would have shown that the cones that remain for several 
years upon this pine open and discharge their seed very promptly upon ripen- 
ing, and that the tree is in no wise dependent upon fire for its seeding —GEo. 
D. Futter. 
Fairy rings and their effect on vegetation.—Of more than ordinary interest 
is a recent paper on fairy rings by SHANTz and PreMEIsEL."” Before taking up 
their own researches, they present an excellent summary of past studies and 
theories ning them, as well as a table of the fungi that have been reported 
as being responsible for rings. Some fungi, as Agaricus tabularis, are very 
destructive to grass and other vegetation; some, as Calvatia and Lycoperdon, 
are beneficial; and some, as Lepiota, have little effect of any sort. in 
conclusions are given relative to the age of rings. The conditions in eastern 
Colorado are not very favorable, either for spore germination or mycelial 
advance; in favorable years there may be a mycelial advance from the ring 
center of 30-60 cm., as compared with almost no advance at all in dry years. 
Some of the rings are very large, and from the growth measurements that have 
been made, a few are estimated to be 400-600 years old. Where vegetation is 
stimulated, it was concluded from careful study that this is due to the reduction 
' of nitrogenous organic matter to available nitrates and ammonia salts, and to 
the subsequent decay of the fungous filaments. Deterioration or death of vege- 
tation are attributed mainly to drought, caused by the prevention of water 
1 SHantz, H. L., and Premetset, R. L., Fungous fairy rings in eastern Colorado 
and their effect on vegetation. Jour. Agric. Research r1:191-246. pls. 21. figs. 5. 
1917. 
