H. BOTANY AND HORTICULTURE. 343 



In this he enumerates twenty-four species of melanosperms, 

 or olive-colored algae, forty-four of rhodosperms, or red algae, 

 and twenty-five of the chlorosperms, or green algae, making 

 ninety-three species in all. The remaining forms, principally 

 microscopic, enumerated by him, and including zygnemaceae, 

 desmideae, and diatoinaceae, bring the number up to one hun- 

 dred and eighty-nine. Of most of these Mr. Olney possesses 

 duplicates, which he will be happy to dispose of in exchange. 

 Pamphlet. 



NEW PARASITE OF THE SPRUCE. 



Much interest has been excited among botanists by the 

 rapid development upon the black spruce and balsam firs of 

 Northern New York of a parasitic plant belonging to the 

 genus ArceuthoMum, related to the mistletoe. In the vicin- 

 ity of Warrensburgh about 75 per cent, of all the Abies were 

 found to be infested, groups of forest trees forty feet in 

 height being dead and bearing the peculiar marks of the in- 

 fection. Dr. Gray remarks that what is curious about the 

 discovery is, first, that it should not have been made before ; 

 and, second, that it should, after all this overlooking, be found 

 during the same season by two persons in three different 

 counties, and so abundant as to disfigure or even to destroy 

 the trees it infests. Bull. Torrey Bot. Club, II., 47. 



INFLUENCE OF HEAT ON PLANTS. 



Hugo de Vries, in a paper upon the influence of heat upon 

 plants, discusses, in the first place, the upward limit of tem- 

 perature for vegetable life, and finds occasion to agree with 

 Sachs, who gives this limit at 120 to 130 Fahr. for the air, 

 and 112 to 117 for the water, although some latitude must 

 be allowed for the age and precise character of the plant. In 

 cases of thermal springs which contain living algae, this limit 

 must, of course, be largely extended, as the result of special 

 adaptation. In reference to the effect of rapid changes of 

 temperature, the author finds that such alternations, however 

 great and rapid they may be, do not exercise any injurious 

 effect upon the vitality of plants as long as they remain be- 

 low the maximum allowable and above the freezing-point, 

 but that such changes do exercise a direct effect upon the 

 movement of the protoplasm by causing its cessation, even 



