712 GENERAL TECHNIQUES FOR CLASSES OF PLANTS 



best made without staining in glycerin or glycerin jelly. Seal 

 with damar balsam, etc. Murray [Bryologist, xxix, 1926, p. 55) 

 puts sections and dissections on a slide into dilute glycerin and 

 covers them. When the glycerin has concentrated by evapora- 

 tion, remove the cover and as much of the glycerin as possible. 

 Melt a little glycerin jelly on a coverslip, place it over the 

 material and keep the cover in place with a small clip. Next 

 heat the slide over a spirit flame until a distinct crack is heard. 

 Cool, remove clip and leave in a formalin bath twenty-four hours. 

 Clean slide and seal. See also Bruch, Ann. Bryol., vii, 1934, 

 p. 6 ; CoNARD, Bryologist, xxxvi, 1933, p. 2. 



Peristomes may also be dried between two slides under a light 

 pressure, moistened with xylol and mounted in balsam. 



Skill in preparing free-hand sections is essential for the deter- 

 mination of species and the interpretation of anatomical features. 

 Henry {Rev. Bryol., lii, 1925, p. 26) recommends that material 

 to be sectioned in elder pith should first be imbedded in celloidin. 

 For cytological studies fix in Flemming or. better, the mitochon- 

 drial fluids. Showalter uses Benda diluted with an equal volume 

 of water or a modified Flemming {Ann. Bot., xl., 1926, p. 713) : 

 200 c.c. 1 per cent, chromic acid, 12-5 c.c. 2 per cent, osmic acid, 

 3 or 6 c.c. glacial acetic acid and 215 c.c. distilled water. 



Most Hepaticfe cut well in paraffin, but many Musci become 

 brittle when prepared by the ordinary method. Use collodion 

 or Zirkle's butyl-alcohol method. 



1403. Culture. Sow spores on soil or, better, on a jelly medium 

 to which nutrient salts are added. Knop's nutrient solution is 

 satisfactory. Menge {Flora, xxiv, 1930, p. 423) grew Mar- 

 chantia and Plagiochasma on agar and silica jelly bases with the 

 addition of nutrient salts. Derring {Verhandl. Naturhist. Ver. 

 Preuss. Rheinlande u. Westfallens, Ixxxv, 1928, p. 306) cultivated 

 Buxbaumia successfully on silica jelly with inorganic nutrients. 

 For Funaria, Schweizer {Ber. Deuts. hot. Ges., xlviii, 1930, 

 p. 75) used agar or sea-sand containing Detmer's solution, brought 

 to the proper acidity by the addition of phosphoric, citric or 

 huminic acids, or mixtures of them. See also Chalaud, C. R. 

 Acad. Sci., Paris, clxxxiii, 1926, p. 612). Bobbins {Bot. Gaz,. 

 Ixv, 1918, p. 543) finds that the addition of carbohydrates (levu- 

 lose, mannose, glucose) to the medium favours growth, especiaUy 

 in the dark. 



PTERIDOPHYTA 



1404. The general histological and cytological methods are 

 suflicient. Sections of root-tips and stem-tips, for apical cells and 

 segmentation must be cut perfectly longitudinally and medianly. 

 Fixation in chrom-acetic, followed by staining with Delafield's 

 hsematoxylin, gives good definition of these. 



Lycopodiales. Leaves and strobili, particularly the older ones 



