Pteridophytes Equisetales 229 



cover with loam, and over this sprinkle a layer of sand about half 

 an inch thick. It does no harm to sterilize everything, but, even 

 then, infection is sure to be brought in with the spores. Con- 

 sequently, it is a good plan to wet the soil and sand with water to 

 which a little permanganate of potash has been added. About 

 five or six small crystals to a liter of water is enough. Wet the soil 

 in this way, then sow the spores, and cover with a pane of glass. 

 Antheridia appear in 3 to 5 weeks. Archegonia appear later if 

 your culture is not destroyed by blue-green algae or fungi (Fig. 75). 



For the development of antheridia, the blepharoplast, and the 

 development of the sperm, fix in Flemming's weaker solution and 

 stain in iron-haematoxylin. The sperm of Equisetum is the largest 

 in Pteridophytes. 



The prothallia are so small that for morphological purposes 

 it is better to mount them whole. With a knife, skim off a thin 

 layer of soil, just thick enough to hold the prothallia together. Fix 

 in formalin or in chromo-acetic acid and stain some in iron- 

 haematoxylin and some in Magdala red and anilin blue. Use the 

 Venetian turpentine method. 



