GENERAL TECHNIQUES FOR CLASSES OF PLANTS 699 



slide between them and the light source. For spores of Rliodo- 

 phyceae, other non-motile spores and eggs of Fucacese, distribute 

 slides evenly over the bottom of the container. As soon as the 

 material is attached, remove the slides to clean water and treat 

 in a manner appropriate to the organisms studied. At intervals, 

 remove slides and invert them flatly upon the surface of the 

 fixative in fixing dishes and treat like a smear. Use fixatives and 

 stains suitable for whole mounts of filamentous algic. 



1388. Charales. Handle like the delicate parts of phanerogams 

 for imbedding, etc. Section branches longitudinally and axially 

 tlirough the reproductive organs. Safranin and anilin blue give 

 a good contrast. Puncture the mature antheridium, stain whole 

 and dissect before mounting. The mature oogonia are difficult 

 to cut. 



1389. Special Storage Products of Algae. Leucosin (Chryso- 

 phyceae) is soluble in most reagents and is unaffected by iodine. 

 It dissolves in water after the cells have been fixed. 



Paramylon (Euglenineae) does not stain with iodine or chlor- 

 zinc-iodide, but is soluble in concentrated sulphuric acid and 

 potash. The grains swell and show a concentric stratification in 

 dilute (6 per cent.) potash, finally dissolving. See Butschli, 

 Arch.f. Protistenk., vii, 1906, p. 197 ; Molisch, Mikrochem., 1923, 

 p. 390. 



Fucosan (Phasophyceae) occurs in the form of vacuolar bodies, 

 insoluble in water and unstained by iodine. It reduces osmic acid, 

 the older vacuoles blackening especially rapidly. Fix with 

 25 per cent. HCl or H.JSO4 and stain with methylen blue. 



Floridean starch (Rhodophyceae) occurs as small doubly 

 refractive granules staining brownish or reddish with iodine. 



FUNGI 



1390. In general treat filamentous fungi like filamentous algae 

 and cut fleshy ones in paraffin. In the case of parasitic forms, 

 however, the nature of the host tissues more often determines the 

 technique than does the fungus. Many Xylariaceae and other 

 fungi become hard and brittle as they mature ; break pieces off 

 and tease them for examination. Cut sections of unimbedded 

 material that has been steeped several weeks in equal parts of 

 95 per cent, alcohol and glycerin. Uredo- and teleutospores of 

 Uredinales require treatment with hydrofluoric acid (1 part to 

 9 parts of water) to remove the silica : otherwise they cut badly. 



MoREAU {Bull. Soc. MycoL, France, xxxiv, 1918, p. 137) is a 

 compendium of mycological methods. 



1391. Culture Methods. See Melhus (Phytopath., ii, 1912, 

 p. 197), for culture of parasitic fungi on living hosts. 



Fungi (saprophytes) are usually cultured in Petri dishes or 



