FERNS. 119 



become mucilaginous. The union of an antherozoid with 

 the oosphere is necessary in order to the subsequent 

 development of the latter. 1 



Developmental History and Minute Anatomy. 2 



The oosphere after fertilization becomes surrounded by a 

 cell-membrane, and is now known as the oospore. It is 

 afterwards divided into two cells by a septum nearly 

 parallel with the axis of the archegonium. This is fol- 

 lowed by the formation of two additional septa at right 

 angles with the first and with each other, the oospore- being 

 thus divided into eight parts or octants. Further cell- 

 division takes place, and the embryo soon shows a differ- 

 entiation into a foot, or absorptive organ, by which it draws 

 nutriment from the prothallium, a first root, leaf, and stem. 

 The first leaf, root, and foot are temporary structures, all 

 of them, serving the needs of the plant for a comparatively 

 short period. The stem, on the other hand, is of slow 

 growth, but is permanent, and finally attains the size and 

 structure that it exhibits in the mature plant; roots and 

 leaves arise from it, the prothallium finally disappears, and 

 the so-called sporophyte takes the place of the preceding or 

 oophyte generation. 



1 Only a bare outline is given above. For further details the student 

 should consult $trasburger, Practical Botany, pp. 290-296 ; Bennett and 

 Murray, Cryptogamic Botany, p. 64 et seq. ; Goebel, Outlines of Classifi- 

 cation and Special Morphology, p. 198 et seq., and references given by the 

 authors just named. For some of the most recent and valuable contri- 

 butions see Campbell, Development of the Ostrich Fern, and various 

 papers by the same author in the Botanical Gazette, Annals of Botany, 

 and other periodicals. 



2 A practical study of the developmental history of ferns requires more 

 time than can possibly be given to it in a preparatory course, and accord- 

 ingly it is thought best to omit altogether directions for laboratory work, 

 merely giving a resume of the cycle of development as it has been worked 

 out by different botanists. Cf. Goebel, I.e., p. 204 et seq. 



