40 Our Native Ferns. 



D. Fecundation of the oosphere developed in the arche- 

 gonium by the antherozoids developed in the antheridium. (Fer- 

 tilization). 



E. Growth of the mature fern in successive stages from 

 the oospore. (Asexual Generation*. Sporophore). 



75. Ophioglossacese. — In this order the prothallia are destitute 

 of chlorophyll, develop under ground and are monoecious, as in 

 the FiLlCES. In Botrychium lunaria the prothallium is an ovoid 

 mass of cellular tissue, light brown without and yellowish white 

 within. It produces a number of antheridia and archegonia on 

 the upper surface as well as the lower, differing somewhat 4-om 

 the true ferns in the method of their development. 



* The term " generation "in tlie above senae, although in common use by the best 

 botanical writers is decidedly unfortunate and misleading. A generation is properly the 

 production of offspring resembling the parent, or the ofEspriug thus produced, which the 

 prothallium is not and the mature fern is not. The generation proper must then be con- 

 sidered as including the entire life history of a fern of which the prothallium and mature 

 fern are successiTe phases. The terms " sexual " and " asexual " as used in this con" 

 nection are likewise misleading as they might apply as well to the origin as to the pro- 

 ducing power of the so-called " generation." The prothallium is asexual in origin but 

 develops sexual organs ; the mature fern on the other hand produces no sexual organs, 

 but is itself the product of bisexuality. I suggest the terms TluiUoid phase and Pteri- 

 doid phase for sexual and asexual generation. The same criticism applies with equal 

 force to the use of the expression " alternation of generations " by zoologists. 



