GENERAL TECHNIQUES FOR CLASSES OF PLANTS 709 



Mycorrhiza are often difficult. Taylor recommends, for roots 

 of Orchidaccjr, fixation in chromacetic and heavy staining with 

 safranin. Destain and counterstain in succession with methyl 

 (or light) green and orange G. The older mycelium and host 

 nuclei stain deep red, the younger mycelium pinkish or green, the 

 host walls yellowish or red (if lignified). 



McLenxan {Ann. Bot., xl, 1926, p. 43) fixes Lolium roots with 

 mycorrhiza in strong Flemming, stains in Heidenhain's haema- 

 toxylin and counterstains with eosin, or else stains in a fuchsin- 

 iodine green combination. She states that roots cleared with 

 carbol-alcohol and examined entire are useful in studying the 

 distribution of the endophyte. 



Rayxer {Ann. Bot., xxix, 1915, p. 97) stained the mycelium in 

 Calluna tissues with a strong solution of cotton blue in lactic 

 acid for eight to twenty-four hours, differentiated in lactic acid 

 and mounted in this reagent or in glycerin ; the material could 

 also be dehydrated and mounted in balsam. Strasburger's 

 orseillin-anilin blue, iron ha-matoxylin and other common stains 

 were also suitable for preparations of the leaves and shoot. 



CoHEX {Stain Tech., x, 1935, p. 25) finds 5 per cent, chromic 

 sulphate (Cro(S04)3 . 15H2O) in 4 per cent, formaldehyde (or 



1 per cent, osmic acid), and saturated with picric or salicylic acids, 

 is best for cytological details as well as proper fixation of the 

 host tissue. Three per cent, acetic acid saturated with orseillin 

 BB and 1 per cent, crystal violet in clove oil is a useful stain 

 combination for infected plant tissue. 



1398. Lichens are often hard to section when imbedded and 

 are best cut unimbedded, using fresh or preserved material. 

 Many of them, as well as the apothecia of Pezizales, etc., may be 

 cut up small, stained in bulk with eosin, rinsed and teased out in 



2 per cent, acetic acid. Or small pieces, stained with eosin, may 

 be dehydrated, cleared in clove oil and teased before mounting in 

 balsam. Fry {Ann. Bot., xl, 1926, p. 397) imbeds corticolous 

 lichens in paraffin after cutting away as much of the wood and 

 secondary cortex as possible without breaking or stretching the 

 bark. Carnoy is a good general fixative, stain in Heidenhain's 

 hsematoxylin with Congo red or erythrosin as counterstain, or in 

 the cyanin-erythrosin combination. See also Fry, Ann. Bot., 

 xli, 1927, p. 437 ; ibid., xHi, 1928, p. 141 ; Pierce, ./. Appl. Micr., 

 i, 1898, p. 99. 



1399. Cotxer's Method for Zoospores {Bot. Gaz., Ixxxix, 

 1930, p. 295 ; Awer. J. Bot., xvii, 1930, p. 511). Kill the zoo- 

 spores in hanging drops on No. 1 coverslips, at the height of their 

 activity, with osmic acid vapour from a 1 per cent, solution of 

 osmic acid. Expose for fifteen seconds to two minutes ; the longer 

 exposure darkens the material, and the shorter one is preferable 

 for details. Then add to the drop an equal volume of a 0-005 per 



