THE AMERICAN ROTANIS'I' 77 



and since tlic fungus is nut present ni every soil, a great num- 

 ber of small seeds enables the species to search the world 

 thoroughly for it in a way that they c<»uld not do if they pos- 

 sessed fewer and larger seeds. 



Acid Soils. — Only a short time ago, no attention was 

 paid to the effects upon plant growth of acids in the soil. Now 

 it is kiKjwn that the presence or absence of such substances 

 profoundly affects the distribution of plants. The principal 

 acids that are regarded as rendering the soil sour are acetic, 

 citric and lactic. Contrary to common opinion, it has been 

 found that the majority of plants favor a slightly acid soil. 

 It is, of course, impossible for the ordinary plants to thrive 

 in soils as sour as those favorable to the growth of heaths, 

 pitcher-plants, and bog-plants generally. In artificial bogs and 

 other plantings of acid-soil plants, tannic acid has often been 

 employctl to give a proper acidity t(^ the soil but since acetic, 

 lactic, and citric acids have been found to have the same effect 

 it might be possible to produce the required acid conditions 

 by the api^lication of vinegar, lemon juice or sour milk. 



Owners of CoMt%KTE Sets. — Since the last report ad- 

 ditional sets of this magazine have been distributed as fol- 

 lows : 



69. F. L. Green, Greenwood, Ontario, Canada. 



70. Amherst College, Amherst, Mass. 



71. Herbier Boissier, Geneva, Switizerland. 



72. Dr. Charles Vetter, 67 West 12 St., New \^ork. 

 7i. W'm. E. Brodersen, 1917 Kllis St., San Franci.sco, 



Calif. 



Mr. Green's set is the second Canadian set ;uid that of 

 tile Herl)ier Boissier the first complete set in Europe. There 

 are now eighteen sets remaining and the price has been ad- 



