PTERIDOPHYTES— FILICALES 



313 



members of the genus, must be sown as soon as ripe, or they fail to 

 germinate. The prothaUia of 0. regalis, if carefully covered with glass, 

 may be kept for a long time, and they become quite large. ProthaUia 

 of this fern in the writer's laboratory produced ribbon-like outgrowths 

 5 mm. wide and more than 5 cm. in length. These prothalha continued 

 to produce archegonia, antheridia, and ribbon-like outgrowths for 

 more than a year, when they suddenly "damped off." Lang watered 







Fig. 102. — Osmunda cinnamomea: photomicrograph of sporangia with spore mother-cells in 

 various stages of division; fixed in Flemming's weaker solution and stained in iron-alum haematoxy- 

 lin; from a preparation by Dr. S. Yamanouchi. Negative by Miss Ethel Thomas. X114. 



prothalha with a weak solution of permanganate of potash, which kills 

 the fungi but does not injure the prothalha. He does not state the 

 strength of the solution, but 4 or 5 crystals to 1 liter of water seems to 

 be effective. Enough should be added to give the water a deep purple 

 color. 



The prothalha of most ferns will grow for a long time under 

 such conditions. Pteris aquilina and many other ferns often fur- 

 nish a good supply of antheridia 3 weeks after sowing, and the 

 archegonia appear soon after, but it is well to make sowings 6 weeks 



