116 



Balsam may be kept from spreading beyond the cover-glass and leav- 

 ing a halo on the finished slide by wiping off the slide with an absorbent 

 cloth close to the sections before putting on the cover-glass. The balsam 

 will then spread to the edge of the cover-glass and stop. 



A small amount of valuable material may be made to serve for a 

 larger number of slides, smaller covers may be used, sections may be 

 Better oriented and worthless sections discarded if sections are examined 

 just after the paraffin ribbons are stretched. Desirable sections may be 

 cut out by rocking a round-edged scalpel. By laying a new slide smeared 

 with fixative on the table in close contact with the original slide, the sec- 

 tions may be transferred to the new slide with the point of a scalpel, 

 after adding a few drops of water to facilitate the moving of the sections. 

 The sections may be more easily examined while in the paraffin if a little 

 Magdala red is added to one of the higher alcohols in which the material 

 is dehydrated previous to imbedding. The small amount of stain ab- 

 sorbed will not affect future staining operations. 



Female gametophytes in pine ovules usually shrink greatly when 

 fixed and imbedded. This may be almost entirely obviated by cutting 

 a slab off each side of the ovule before it is fixed. A Gillette razor 

 blade is very satisfactory, since on account of its thinness it does not 

 crush the material. 



Seeds of the pinyon pine (Pinus edulis) are very satisfactory to 

 illustrate the gross anatomy of the gymnospeim seed, since they are 

 very large and easily dissected. The gametophyte and contained embiyos 

 or the embryos alone may be dissected out, soaked in water a short time, 

 fixed and imbedded. They cut very easily. 



A modification of Land's Fixative (See Botanical Gazette, Vol. LIX, 

 page 397), has been used very successfully for refractory sections that 

 will not adhere readily with egg albumen. Land's fixative dries very 

 quickly, causing the liquid added to float the sections to spread with 

 difficulty. By using the following formula, the liquid spreads as easily 

 as with egg albumen: 



2?c gum arable in water 50 c. c. 



Glycerin 50 c. c. 



Sodium salicylate 1 gram. 



