March 14, 1902.] 



SCIENCE. 



403 



Wood's Holl, Mass., during portions of the 

 last three summers. The plant most used 

 was Cladophora gracilis. This alga was 

 able to survive temporarily in a cane-sugar 

 solution containing 1.2 gram molecules per 

 liter of solution Avithout apparent injury, 

 and carried on its functions with seeming 

 regularity. A greater or less proportion of 

 the cells lived in concentrations between 

 0.3 grm. mol. and 1.6 grm. mol., but at 

 the extremes unbalanced osmotic forces 

 wrought injury to the younger cells. The 

 plants were fatally affected within an hour 

 by solutions of sodium ehlorid in all con- 

 centrations, and in a solution isotonic with 

 sea water were unable to respond to plasmo- 

 lytic tests after about one-half hour. A 

 progressive synthesis of artificial sea water, 

 containing those substances present in a 

 quantity equal to five thousandths of one 

 per cent., was made. Death in a solution 

 containing the proper amount of sodium 

 ehlorid took place in about a half-hour. 

 When to this magnesium salts were added, 

 no marked change in the period of survival 

 was seen. The addition of the trace of 

 calcium sulfate required extended the time 

 of survival to about two hours. On the fur- 

 ther addition of the potassium compounds, 

 the plants lived for about twenty-four 

 hours. Although isotonic -with natural sea 

 water, this artificial mixture was less saline 

 to the taste than the former. On adding 

 further sodium ehlorid (about three- 

 fourths per cent.) until equal salinity to 

 the taste was obtained, the artificial solu- 

 tion was found to be capable of supporting 

 an apparently normal existence in the alga 

 for eight days. Evidence that cannot be 

 summarized here was presented in support 

 of the view that not only the actual amount 

 of substances dissolved is concerned in the 

 physiological behavior of sea water, but 

 that the form in which these things there 

 exist is important. Further work is in- 

 progress. 



On the Teaching of Plant Physiology to 

 Large Elementary Classes : Professor W. 

 F. Ganong, Smith College. 

 The author called attention to the fact 

 that the advance of science depends not 

 only upon the acquisition of new knowledge 

 and its correct interpretation, but also upon 

 its utilization, of which one phase is its 

 application in education. Plant physiology 

 is rapidly rising in educational favor, but 

 a chief obstacle to its more rapid advance 

 is the difficulty of teaching it to large 

 classes by proper laboratory methods. It 

 was pointed out that many of the practical 

 difficulties are disappearing with the im- 

 provement in methods and appliances, and 

 ultimately the subject will be taught 

 through individual experimentation. This 

 is not yet practicable in large elementary 

 classes, and at present students must be 

 taught en masse. After trial of various 

 plans the author had attained fair success 

 b}^ selecting the ten or twelve most funda- 

 mental experiments and setting them up, 

 with full explanations, before the class, re- 

 quiring the students individually to make 

 records and finally to present reports upon 

 them. The details of the management of 

 the plan on which its success largely de- 

 pends can not be repeated here, but the 

 paper is soon to be published in School 

 Science. 



Discussion on the Most Profitable Rela- 

 tion of the American Botanical Societies 

 to one another. 



The opinions brought out by this discus- 

 sion agreed very closely with those ex- 

 pressed by the speakers before the Ameri- 

 can Society of Naturalists at Chicago on 

 January 1, as reported in this journal for 

 February 14. One speaker urged a closer 

 union of the various societies with the 

 American Association, while another ad- 

 vocated the merits of a double system, in 

 which regional societies, meeting regularly 



