[Vol. Vi, No. 1, 
^90 
The Ohio Naturalist. 
V. Pteridophyt.v, Heterospor.\e. Heterosporous Pterido- 
])hvtes. 635 known living species. 
Plants in which the sporophyte, in the living species, is herbaceous 
and after a brief embryonic stage has an independent e.xistence with 
true fibro- vascular tissue, roots, and leaves; heterosjDorous, with micro- 
spores and megaspores which give rise to greatly reduced male and female 
gametojjhytes respectively; eusj)orangiate or leptosporangiate, Gametcj- 
phytes always unisexual, with little or no chlorophyll, living on food 
stored in the spore and developing entirely inside of the spore wall or 
])rotruding only slightly through the side, the nonsexual spores often 
germinating liefore being discharged. 
VI. Gymnosperm.ve. Gymno.sperms. 450 known living 
species. 
Plants in which the sporophytes are woody perennials with open 
carpels (megasporophylls) without a stigma and hence with naked ovules 
and seeds, the ]>ollen (male gametophvte) falling directly on the micro- 
jjyle of the ovule (megasporangium) ; flowers monosporangiate, usually 
developing as cones but sometimes very simple; female gametophvte 
with numerous cells but without polar cells and thus without true endo- 
sperm as in the Angiosperms; male gametophyte much reduced but 
usually with vestigial vegetative cells; male cells two, either nonmotile 
sperms or developed as spirally coiled multiciliate spermatozoids. 
VII. AxGiosPER.M.tE. Angiosj)erm.s. 125,000 known living 
species. 
Plants in which the sporophytes are of diverse habit, from minute 
annual or perennial herbs to large trees; ovules in a closed carpel (mega- 
sporophvll) or set of carpels provided with an ovulary and with a stigma 
for the reception of the pollen (male gametophyte) which must develop a 
long pollentube, usually passing through the open cavity of the ovulary, 
before reaching the micropyle; flowers more commonly showy and highly 
specialized anel more cejinmonly bisporangiatc ; female gametophyte 
greatly reduced, normally with eight cells two of which, the polar cells, 
conjugate to form the definitive cell from which the endosiserm is devel- 
oped; male gamete)phyte consisting of three cells two of which are non- 
motile sperms, one used for fertilization and the other in many cases 
uniting with the definitive cell thus producing a triple fusion. 
