168 THE AMERICAN BOTANIST 



cording to an article by Vernon Bailey in Journal of Agri- 

 cultural Research, the meadow mouse begins to breed when 

 but twenty-five days old and may produce from thirteen to 

 eighteen families wathin a year, each family consisting of 

 from four to nine individuals. If all the young should breed 

 and none should die, it is estimated that the descendants of 

 a single pair might number more than a million in a year. 

 It is doubtful if man could carry on bis cultivation of the 

 soil without the aid of the birds and other animals that prey 

 on the mice. However mice may have their uses. Seton 

 has called them "the boats designed to bring over food from 

 the mainland of grass to the island of carnivores." 



Resistant Chestnuts. — The chestnut tree, one of the 

 most interesting and ^•aluable in the American forest, is 

 practically extinct in the Northern and Eastern States. This 

 has been caused by a virulent plant disease, the chestnut 

 blight, whose microscopic spores, blown about in vast quanti- 

 ties, have sought out the chestnuts, wherever growing, and 

 in spite of all man's efforts have killed the trees. In many 

 places the forest is heavily depleted, the trees still standing 

 but brown and dead. The blight, however, seems often to 

 have killed only the aerial parts and there is a fine growth of 

 sprouts from the roots, in some cases more than ten feet 

 high. Whether the blight will return and ultimately kill this 

 new growth, or whether an occasional plant w?ill prove re- 

 si stent enough to triumj)!! over the blight and supply material 

 tor reforesting the country remains to be seen. In the Sus- 

 quehanna Valley of southern New York the writer was sur- 

 prised and pleased to find a single tree as fresh and green 

 as ever, standing in full bloom in the midst of. the surround- 

 ing desolation. The case of the chestnut emphasizes the 

 danger to American plants of introducing foreign species. 

 The blight undoubtedly came from imported Japanese chest- 



