MALE FERN. OOPHORE OR PROTHALLUS. 207 



a. A wall, composed of a single layer of narrow 

 cells ; this completely surrounds 



I. The mother-cells of the Antherozoids, which 

 are small, and not very numerous. 



Other antheridia may be found which have already 

 burst the outer wall; in these the contents of the 

 mother-cells may perhaps be seen escaping from the 

 ruptured antheridium as spiral Antherozoids, endowed 

 with active movements. 



If a preparation showing motile antherozoids be treated with a 

 weak solution of iodine, the movements will cease with, the death 

 of the antherozoids, which will assume a brown staining, while 

 the cilia attached to the anterior ends of. them will then be 

 clearly seen. 



Select under the low power one mature Archego- 

 niurn, and then observe it in detail under the higher 

 power. If the neck be vertical, which would under 

 the circumstances be the natural position, there will 

 then be seen, on focussing down upon it, four cells 

 composing the wall of the neck, and surrounding one 

 cell, the Canal cell. 



IV. Treat some prothalli with a saturated solution of 

 picric acid in water for some hours. Wash them with 

 water, and then harden them gradually by successive 

 treatment with alcohol of 50 per cent., 70 per cent., 

 and finally with absolute alcohol or strong methylated 

 spirit. [N.B. The preparations described below may 

 also be made from fresh material, but the results will 

 not be nearly so good as if the above method of fixing 

 and hardening be adopted.] 



Hold a prothallus thus prepared between pieces of 

 pith, or imbed as directed on p. 4 &c. ; then cut 



