APPENDIX VI 697 



when acetic acid is applied without the preceding application of the alcohol. The 

 identification of the "unknown" moulds can be made by the use of the following 

 key, which is a translation of the one given by Lindner in his work on the Swiss 

 moulds, and which includes most of the important moulds of the world. Pure 

 cultures of various moulds can be obtained from Johanna Westerdijk, Director of 

 the Phytopathological Laboratory, Amsterdam, Holland; from Krai's Bacteriologis- 

 chen Laboratorium, Prague, Bohemia, i., Kleiner Ring, 11; and from Mrs. Flora 

 W. Patterson, Bureau of Plant Industry, Washington, D. C. Some of them can be 

 obtained by exposing various articles to the air under a bell jar with filter paper. 

 Transfers of these moulds to fresh culture media should be made every two or three 

 months. During the summer and even during the winter the cultures can be kept 

 on ice in a refrigerator, so that the transfers need not be made so frequently during 

 the hot weather of the summer, or while the teacher is off on his vacation. The 

 janitor should be instructed to look after the ice supply during the year. Cf . Povah, 

 A. H. W.: A Critical Study of certain Species ofMucor. Bull. Torr. Bot. Club, 

 44: 241-259, May, 1917, continued. 



Key for the Determination of Species of Mucor 



Sporangiophores not branched, i Group Mono-mucor. 

 Sporangiophores branched. 



(a) Branches rare, or more numerous and indefinite, in racemes, or corymbs. 



2 group Racemo-mucor. 

 (h) Branches definite in sympodia. 3 Group Cymo-mucor. 



I Group Mono -Mucor 



Sporangiophores unbranched. (E.xceptionally unless the conditions of nutrition 

 are unfavorable, they form branches. These are anomalous cases.) 



1. Sporangiophores at first erect, afterwards weak, finally drooping and trans- 

 formed into a woolly felt of a rusty color, i M. rufesccns Fischer. 

 Sporangiophores always erect and forming a matted growth. (2) 



2. Sporangiophores never exceeding 2 cm. (3) 

 Sporangiophores longer than 2 cm. (7) 



3. Sporangiophores never e.xceeding 300 /j.. (4) 

 Sporangiophores exceeding o 5 cm. (maximum 2 cm.). (5) 



4. On solid media matted growth very short, velvety, color at first brownish 

 red-carmine then grayish, sporangia small (20;u maximum). 2 M. Raman- 

 niamus MoUer. 



Matted growth scarcely visible, sporangiophores 210^1, colorless, septate; 

 sporangia 40 to 45^l diameter. 3 M. siibtilissimus Oudemans. 



5. Wall of sporangium not diffluent; on breaking it leaves an irregular, ragged 

 collarette, sporangia 36 to 42yu diameter, spores elliptic 6/x by 8^. Matted 

 growth 1.5 tall. 4 M. hygrophiliis Oudemans. 



Wall of sporangium not diffluent, sporangia large, 80 to q8;u in diameter, 

 spores elliptic s^u by Sju. 



