NOVEMBEE 11, 1898.] 



SCIENCE. 



655 



in which the majority of a number of fila- 

 ments of Spirogyra survived, after an ex- 

 posure of twenty- four hours, was regarded 

 as the measure of the osmotic action which 

 the alga can endure. This boundary con- 

 centration was found to lie at 0.75 gram 

 molecules per litre. Assuming the action 

 of the other substances studied, viz.: glycer- 

 ine, potassium nitrate and sodium chloride, 

 to be likewise purely osmotic, the boundary 

 concentrations were calculated to lie as 

 follows : glycerine, 0.75 gram molecules per 

 litre; potassium nitrate, 0.45 gram mole- 

 cules; and sodium chloride, 0.47 gram mole- 

 cules. The actual boundary concentrations 

 found by the method used for sugar were as 

 follows : glycerine, h gram molecules per 

 litre ; potassium nitrate, y^^ gram molecules ; 

 and sodium chloride, -^-^ gram molecules. 

 The concentrations producing plasmolysis 

 were as follows ; glj'cerine, ^^ gram molecules 

 per litre ; potassium nitrate, J gram mole- 

 cules ; sodium chloride, ^ gram molecules ; 

 and sugar, i} gram molecules. The bound- 

 ary concentration for glycerine lies at a 

 concentration greater than that of the cell 

 sap, and probably causes death by osmotic 

 action. The boundary concentrations 'of 

 potassium nitrate and sodium chloride lie 

 much below the point having the same os- 

 motic value as the cell sap, and much be- 

 low the boundary concentration calculated 

 on the assumption of purely osmotic action. 

 Consequently, potassium nitrate and sodiuni 

 chloride exert a pronounced toxic influence 

 upon Spirogyra. 



Types of Vegetation on the Florida Keys. C L. 



POLLAED. 



Paper, partly ecological, partly floristic. 

 Six distinct belts or zones of plant life are 

 recognized. The main part of the paper 

 consisted of an enumeration and discussion 

 of the characteristic species of these belts, 

 as observed during a six weeks' visit in the 

 spring of 1898. 



Potato as a Culture Medium with some Notes on 

 a Synthesized Substitute. De. Eewin F. 

 Smith. 



The length of this report makes it seem 

 best to relegate the abstracts of my own 

 papers, which are long and rather technical, 

 to the forthcoming volume of the Proceed- 

 ings of the Association, where they may be 

 found by those who desire to consult them. 



Some Little Used Culture Media, which have 

 proved valuable for Differentiation of Species. 

 De. Eewin F. Smith. 



The Temperatui'C and Transpiration of Desert 

 Plants. Peofessoe D. T. MacDougal. 

 The author reported data taken from 

 field notes made in the desert of the Little 

 Colorado River in 1898. 



The temperatures of the bodies of suc- 

 culent plants in this region at midday is 

 often as high as 45° C, the critical point of 

 protoplasm, and 6° to 8° higher than the 

 surrounding air. The enormous transpir- 

 ing force exerted is met by the high-soil 

 temperature, which in volcanic sand reaches 

 40° to 42° C. around the absorbing roots. 

 The actual amount of water used by desert 

 plants, when furnished with an unlimited 

 supply, is very small, however. By use of 

 a potometer it was found to be not more 

 than one-tenth as much as from a cor- 

 responding mesophyte of temperate lati- 

 tudes. Desert plants are, therefore, in- 

 capable of great transpiratory or absorptive 

 activity. 



The Leaf-spot Disease of the Apple, Phyllosticta 

 pirina, and Several Unrelated Forms occur- 

 ring therewith. Peofessoe Wm. B. Al- 



WOOD. 



Papee records common occurrence and 

 life cycle of Phyll. pirina Sacc. and the oc- 

 currence therewith of three apparently un- 

 related forms, viz.: Sphwropsis malorum, 

 Hendersonia mali, and an undetermined 

 species. 



