PTERIDOPHYTES— FILICALES 321 



holic corrosive sublimate-acetic acid, formalin (4 g. corrosive subli- 

 mate, 5 c.c. formalin; 5 c.c. acetic acid, 100 c.c. of 50 per cent alcohol) 

 can be recommended for both Azolla and Salvinia. Both of these 

 forms grow well in the greenhouse, floating on the water in tanks or 

 aquaria; but Azolla seldom fruits under such conditions. Salvinia 

 sometimes produces microsporangia in the greenhouse, but megaspo- 

 rangia are comparatively rare. 



