240 Proceedings of Indiana Academy of Science 



rhizoids. Growing prothallia for longer periods of time than obtains 

 under natural conditions out of doors, however, requires experience to 

 insure success. 



Fertilization or Fecundation. — When the plants have attained the de- 

 sired size — eight to ten millimeters in width — fecundation should be 

 begun. If the prothallia be monoecious, three or four drops of water 

 are allowed to fall upon the growing notch. It is better to do this near 

 mid-day when the cultures are a little drier, as the mature archegonia 

 will then open readily, and at the same time sperms will escape from 

 the antheridia. This procedure should be repeated every other day for 

 a few times, so that several egg cells may be fecundated upon a given 

 prothallium. 



If the prothallia tend to be dioecious, as in Onoclea se7isibilis and 

 Matteuccia StrufJiiopteris (Onoclea Stmthiopteris) , it is well to place a 

 small tuft of male plants close to the apical sinus before dropping on 

 the water, in order to insure fecundation. 



