238 



Methods in Plcmt Histology 



cluced ribbon-like outgrowths 5 mm. wide and more than 5 cm. in 

 length. These prothallia continued to produce archegonia, anther- 

 idia, and ribbon-like outgrowths for more than a year, when they 

 suddenly "damped off." Lang watered prothallia with a weak 

 solution of permanganate of potash, which kills the fungi but does 



B 



FIG. 79. Pteris aquilina: A, filamentous stage; B, the apical cell has been estab- 

 lished and several segments have been cut off; the figure shows the initial rhizoid and 

 also three rhizoids coming from the main body of the prothallium ; C, an older prothallium 

 covered with antheridia in various stages of development; from a drawing by Miss 

 M. E. Tarrant. 



not injure the prothallia. He does not state the strength of the 

 solution, but four or five crystals to a liter of water seems to be 

 effective. 



The prothallia of most ferns will grow for a long time under such 

 conditions. Pteris aquilina and many other ferns often furnish a 



