504 



Journal of Applied Microscopy. 



Uiicinula iiecator. — The mildews are found throughout the summer and 



autumn on the leaves of 

 various plants. The lilac 

 mildew (^Miirosphcera ahii) 

 and the mildew on the 

 Virginia creeper ( i'luimila 

 necator) are particularly 

 abundant. For herbarium 

 purposes they may be pre- 

 served by simply drying 

 the leaves under light 

 pressure. When mounted 

 for examination, the leaf 

 should be soaked in water 

 for a few minutes, after 

 which the perithecia may 

 be scraped off and mounted 

 in [water. The asci may 

 then be forced out by 

 pressing smartly on the 

 cover. 



For permanent mounts 

 of entire perithecia with 

 appendages, fix in three 



Kig. 2Q. 



A. Uucinula necator on Aii!/>e/o/>sis qiiiiiqucfolia. '■' 192. Four asci 

 containing ascospores have been forced out by pressing on the cover. 

 Fixed in hot corrosive sublimate, stained in fuchsin and mounted in 

 balsam. B, a conidiospore ; and C, an appendage of Microsf^hiera nhii, 

 drawn from living material. ■ iq2. 



per cent, formalin twenty-four hours, wash in water one hour, stain in aqueous 

 eosin twenty-four hours, treat with one per cent, acetic acid one minute, wash 

 thoroughly in water, and then transfer to ten per cent, glycerine, which should 

 be allowed to concentrate as usual. 

 If chromic acid or corrosive sublimate 

 be used for fixing, the appendages 

 become brittle, and very easily break 

 off. However, the chromo-acetic 

 mixtures are better if it is desired to 

 make paraflfin sections showing the 

 development of the perithecium witli 

 its asci and spores. For this purpose 

 the omnipresent ErysipJie loiiniiiiiic on 

 Polygonum ai'/cii/a/r is exceptionally 

 favorable because, after the material 

 is lixed and in alcohol, the whole my- 

 celium, with the developing perithecia, 

 may be stripped from the leaf without 

 the slightest difficulty, thus avoiding 

 the necessity of cutting the leaf in 

 order to get the fungus. Delafield's 

 ha;matoxylin gives good results. A 



lOUR APPMIC 



Xy/arin. 



Transverse section of a young stroma showin.g perithecia. 

 8. Fixed in chromo-acetic acid, stained in bulk in 

 alum carmine, imbedded in celloidin, and mounted in 

 balsam. H. Two asci with spores. ■ 245. The 

 mature stroma was soaked for several days in equal 

 parts of 95 per cent, alcohol and glycerine, and then 

 imbedded in celloidin. Not stained. 



