106 



loosely under the lens for examination, and after it has served the purpose of the 

 moment is brushed aside and lost, or at best preserved in packets ujjon the sheet 

 with the specimen from which it was taken. This method is mussy and eventually 

 impairs the mounted specimens of an herbarium, and where there are many 

 workers it is not economical of time. To avoid this is quite practicable through 

 the preservation of all such materials dry in cells upon glass slips as opaque 

 mounts for the microscope. The cells are built by gluing to the glass slips 

 brass ring^, and the specimens are enclosed by cementing to the top of this ring 

 the ordinary circular cover glass. The method of building this form of cell was 

 suggested by Dr. Griffiths some years ago and is quite familiar. A cell of this 

 form will not accommodate leaves and some other plant structures as well as an- 

 other form of cell, which is made by gluing a rectangular frame cut from cardboard 

 to the glass slip. A cell of this construction will contain small leaves entire or 

 the tip and basal portions of larger leaves, which can be viewed from either side. 

 A cell of this type must be enclosed by a rectangular cover glass. A supply of 

 slips, upon which cells of various sizes have been built, may easily be kept on 

 hand, and whenever it becomes necessary to remove from an herbarium specimen 

 material for examination, it may be placed in a cell in manner best adapted for 

 its display, labeled, and you have at once, at very small expense, a slide of veg- 

 etable material which will be ready for use at any future time; and, if such a 

 collection of slides is properly classified and arranged, it forms a working ad- 

 junct to the herbarium of much value, and, besides, provides one constantly with 

 available material for numbers of demonstrations in botanical work. 



H.KMAGLOBIN AND ItS DERIVATIVES. IJy A. .J. BiGNEY. 



On subjecting a dilute solution of arterial blood to spectroscopic examination, 

 certain parts of the spectrum of natural or artificial light will be absorbed. The 

 amount of this depends upon the degree of concentration of the blood ; if a one 

 per cent, or two per cent, solution be used, two narrow dark bands are seen in the 

 orange-yellow between the Frauenhofer lines D anii E, the one next to E being a 

 wider, but not so deep a band as the one next to D. A little of the red is absorbed 

 and the violet, indigo, and a part of the blue. This is the spect-rum of Oxy. -Haem- 

 oglobin. 



If arterial blood or venous blood which has been shaken with air be treated 

 with some reducing agent such as ammonium sulphide or alkaline iron sulphate 

 with tartaric acid, a decided change occurs in the spectrum, instead of the two 



