r 



1920] BRIEFER ARTICLES 319 



This raises the question as to the effect of the composition of the 

 soil solution upon the amount of easily freezable water in plant tissue. 

 Possibly we shall be able to present results of experiments dealing with 

 this question at a later date. It seems that the amount of water that 

 readily freezes in the roots, stems, leaves, fruits, and seeds of plants and 

 the factors that affect the freezing should be of general interest, at 

 least to the physiologist, and it is probable that a knowledge of it would 

 be valuable especially w r here the changes in the concentration of the cell 

 contents of plants as well as winter injury are being investigated. 



The difficulty encountered in causing tissues to solidify at the higher 

 temperatures, especially when small amounts are used in the determina- 

 tions, raises some important questions relative to winter injury of plants 

 grown in different soils. It is possible and probable that some soils 

 do not solidify, although the temperature may go appreciably below 

 the freezing point. It is very easy to cause a sandy soil to solidify 

 without much supercooling; with clay it is more difficult; while it 

 is far more difficult in case of muck or peat. Instances have been 

 observed where fruit trees growing in sandy soils have been severely 

 injured by low temperature, while those growing in adjacent soils largely 

 escaped. It is true, however, that sandy soils are more responsive to 

 air changes than are the finer textured ones. — M. M. McCool and 

 C. E. Millar, Michigan Agricultural College, East Lansing, Mich. 



ISOLATING SINGLE SPORES 



(with one figure) 



A new method of isolating single spores has been devised, which 

 differs from other methods in common use in the substitution of a 

 mechanical method of marking the location of the spores in the poured 

 plates for the usual procedure of marking with ink-dots under the micro- 

 scope. A cylinder of brass about the length of the ordinary 1.9 mm. 

 objective is turned in the form shown in fig. 1, one end being provided 

 with a thread like that of the objectives of the microscope to be used, 

 and the other turned down and the end hollowed out so as to form a 



tube of the size desired. 



This device is then screwed into the revolving nosepiece of the 

 microscope in place of one of the objectives. The cover is now removed 

 from the Petri dish containing the poured plates, and the spores are 

 located under the microscope. When 



tive, the tip of the marker is sterilized by flaming it with a gas burner 



or alcohol lamp, the nosepiece is rotated so as to bring the marker 







