BOTANICAL GAZETTE. 91 



Prof. J. C. Arthur reports a very successful session of the Sum- 

 mer School iit the University of Minnesota. There were forty stu- 

 dents at work in the botanical laboratory and all were enthusiastic, 

 as might be expected. For the benefit of botanists who suppose 

 that some distant locality furnishes better illustrations for study 

 than home plants, and who so often connect the lower forms with 

 something distant and unattainable, we quote the following from 

 Prof. Arthur's private letter: 



" We found Cham wherever we went. There was an equal 

 profusion of Xostocs, and Desmids. Nitella, Vaucherkt-, Vokox, Hy- 

 (I rod id i/oii and Mesocarpus were specially abundant. Numerous 

 large and handsome slime-moulds were found on the side-walks, 

 and we were also able to study every stage of the polymorphous 

 JPuccinia, even to the germination of the teleutospores." 



The current " Part " of the Proceedings of the Philad. Acad. 

 Sci. contains two papers of botanical interest, both by Mr. Thos. 

 Meehan,whose restless eyes and pen are ever observing and recording. 

 In one of them is recorded the fact that Salisburia adiantifolia is 

 sometimes hermaphrodite; while in the other, which is a much 

 more formal paper, are recorded some observations 011 the relation 

 of heat to the sexes of flowers, based chiefly on a study of the ma- 

 ple and which concludes with the following generalizations: 



Male flowers do not appear on female maple trees till some of its 

 vital power has become exhausted. 



Branch-buds bearing female flowers have vital power sufficient 

 to develop into branches. 



Branch-buds bearing male flowers have not vital power enough 

 to develop into branches, but remain as spurs which ever after pro- 

 duce male flowers onl}\ 



Buds producing male flowers only are more excited by heat 

 than females, and expand at a low temparature, under which the 

 females remain quiescent. 



Prof. H. Baillon, wishing to germinate some seeds of walnut 

 and almond trees in winter, thought to obtain a more rapid devel- 

 opment in a warm house in which the temperature varied during 

 the twenty-four hours from 15° to 25° (59-77 F.) than in a cool 

 house in which the daily variation was between 5° and 15° (41-59 F. ), 

 but the trial failed. In the cool house in the course of six weeks 

 the walnuts had steins of about two decimeters in height, while 

 the most advanced in the warm house had stems of only two or three 

 centimeters. At the end of two months and a hall the seeds grow- 

 ing in the warm house had roots only occasionally well-developed, 

 but little or no caulome outside the fruit. When walnuts were 

 germinated in a warm house with "bottom heat" the tap roots were 

 early arrested in their development though growing in a very fria- 

 ble soil consisting of moist sawdust; whereas when germinated in a 

 cool house, without bottom heat, the tap roots grow well in length 

 before the egress of the plumule. The same results were obtained 



