November 24, 1916] 



SCIENCE 



759 



natural condition of the structure is main- 

 tained, there being but little shrinkage. Cell 

 contents relatively insoluble in water, but sol- 

 uble in xylol and oils, are not lost. Sections as 

 thin as 10 microns can be cut with ease. How- 

 ever, serial sections can not be cut, nor can 

 some stains be used unless the gelatine is dis- 

 solved away after sectioning, which is not easy 

 to do. The method is as follows: Ordinary 

 cooking gelatine is soaked two or three hours, 

 or until it will absorb no more water, then 

 after the excess of water is poured off it is 

 warmed until melted. A temperature of not 

 over 70 degrees Centigrade should be main- 

 tained. Part of the liquid gelatine is now 

 thinned with an equal volume of water and the 

 material to be embedded is kept in this dilute 

 gelatine for several hours, during which it 

 must be warm enough to remain liquid. Fol- 

 lowing this, concentrated gelatine is used 

 similarly for several hours more. The dishes 

 containing the material being embedded 

 should be corked to prevent drying. The ma- 

 terial is now cooled in a paper tray coated 

 with paraffin, after which it is hardened for 

 several days in 4 per cent, formalin. The 

 microtome knife must be sharp, with no bevel 

 on the lower side, and set at as great an angle 

 as possible. Either alcohol or water may be 

 used to flood the knife in cutting. Pieces of 

 the gelatine with embedded material are, as a 

 rule, strong enough to be clamped in place in 

 the machine without wooden blocks as sup- 

 ports. 



Materials which can not be cut otherwise 

 yield easily to the knife after the use of dilute 

 or concentrated hydrofluoric acid 4 for one to 

 three weeks, which is followed by thorough 

 washing in water, then the regular paraffin 

 method. Ample time for each stage of the 

 paraffin method to permit dehydration and em- 

 bedding of the large pieces must be given. 



Acknowledgment for many suggestions is 

 made to Dr. L. L. Burlingame, of the botany 

 department of Stanford University. 



Kearn B. Brown 

 Stanford University 



* Bailey, I. "W., " Microtechnique for Woody 

 Structures," Bot. Gaz., Vol. 49, January, 1910, 

 p. 58. 



THE ECOLOGICAL SOCIETY OF 

 AMERICA 



A meeting of the Ecological Society of Amer- 

 ica was held in the High School building at San 

 Diego, California, on August 10 and 11, 1916, and 

 two joint sessions were held with the Western So- 

 ciety of Naturalists. About twenty-five members 

 were present, the chair being occupied by the sec- 

 retary-treasurer. Members of the society partici- 

 pated in the biological dinner at the U. S. Grant 

 Hotel on the evening of August 12. On the after- 

 noon of that day the work of the Scripps Institu- 

 tion was demonstrated by members of its staff. On 

 August 13 and 14 the members of the Ecological 

 Society were guests of the San Diego Society of 

 Natural History on a 200-mile automobile trip to 

 the Cuyamaca Mountains and the edge of the 

 Colorado Desert. 



Following are abstracts of papers presented at 

 the sessions of the society: 

 The First Stage in the Secession of the Salton 



Sea: D. T. MacDougal. 

 The Trees and Shrubs of the Grand Canyon of the 



Colorado: Alice Eastwood. 



The zones of plant life in the Grand Canyon 

 may be defined by the trees and shrubs which 

 characterize them. The great diversity of en- 

 vironment results in complexities of distribution 

 which offer a promising field for ecological in- 

 vestigation. Fifty lantern slides were shown, made 

 from herbarium specimens of the leading trees 

 and shrubs of the Canyon, collected on the Bright 

 Angel, Hermit and Berry trails. 



Besults of the Effect of Chaparral and Forest 



Cover on Meteorological Conditions: Edward N. 



Munns. 



Becords have been taken daily at three stations 

 at the Converse Experiment Station, for three 

 successive years. One station is located in an 

 open cienega, one in a chaparral field, the third in 

 a forest of Jeffrey pine, all stations being about 

 6,000 feet elevation. 



The records show the mean annual temperature 

 under the chaparral cover is 2°.8 higher than in 

 the open, and that of the forest 1°.2 higher. More 

 important are the extremes, the mean maximum 

 in the chaparral, being 5°. 7 higher and the mean 

 minimum 2°.0 lower than in the open, while the 

 mean maximum under forest conditions is 1°.4 

 lower and the mean minimum 3°. 8 higher than in 

 the open. The mean daily range in the open is 

 26°. 5, that of the chaparral 7°. 7 greater, and that 

 in the forest 5°.2 less. 



Soil temperatures are greatest in the open, and 

 least in chaparral with a difference of 1°.0 be- 



