39<3 The Ohio Naturalist. [Vol. Vl, No. 1, 



V. Ptekidophvta, Heterosporae. Heterosporous Pterido- 

 phvtes. (Jo") known living species. 



Plants in which tlie sporophyte, in the hvinj^ species, is herbacecnis 

 and after a brief embryonic stage has an independent existence with 

 true libro- vascular tissue, roots, and leaves; heterosporous, with micro- 

 spores and megaspores which give rise to greatly reduced male and female 

 gametophvtes respectively; eusporangiate or leptosporangiate. Gameto- 

 phytes alwavs unisexual, with little or no chlorophyll, li\'ing on fcjod 

 stored in the spore and developing entirely inside of the spore wall or 

 protruding only slightly through the side, the nonsexual spores often 

 germinating before being discharged. 



VI. Gymnospermae. Gymnosperms. 450 known living 

 species. 



Plants in which the sporophytes are woody perennials with open 

 carpels (megasporophylls) without a stigina and hence with naked ovules 

 and seeds, the pollen (male gametophvte) falling directly on the micro- 

 pyle of the ovule (megasporangium) ; flowers monosporangiate, visuall\- 

 developing as cones but sometimes very siniple; female gametophvte 

 with numerous cells but without polar cells and thus without true cnrlo- 

 sperm as in the Angiosperms; male gametophyte much reduced but 

 usuallv with vestigial vegetative cells; male cells two, either nonmotile 

 sperms or developed as spirally coiled inulticiliate spermatozoids. 



VII. Angiospermae. Angiosperms. 125,000 known living 

 species. 



Plants in which the sporophj^tes are of diverse habit, from minute 

 annual or perennial herbs to large trees; ovules in a closed carpel (mega- 

 sporojjh'i'll) or set of carjxls provided with an ovulary and with a stigma 

 for the reception of the pollen (male gametophyte) which must develop a 

 long poUentube, usuall_v ])assing through the open cavit\' of the ovulary, 

 before reaching the micropyle; flowers more commonly showy and highly 

 specialized and more commonly bisporangiate ; female gametophyte 

 greatly reduced, normally with eight cells two of which, the polar cells, 

 conjugate to form the definitive cell from which the endosperm is de\'el- 

 oped; male gairietophyte consisting of three cells two of which are non- 

 iTiotile sperms, one used for fertilization and the other in many cases 

 uniting with the definitive cell thus ]iroducing a triple fusion. 



