Division I. Pteridophyta 



Ferns and Fern Allies 



Terrestrial, epiphytic, saxicolous or occasionally aquatic plants with a life cycle 

 of two distinct phases — Sporophyte and Gametophyte. The sporophyte is usually 

 differentiated into root, stem and leaf provided with vascular tissue (phloem and 

 xylem), and produces spores asexually that are either alike (plants homosporous) 

 or of two very unlike kinds called microspores and megaspores (plants heteros- 

 porous). The spores germinate to produce the gametophyte or minute incons- 

 picuous sexual stage (prothallium). In the homosporous series the prothallia are 

 similar but may be either monoecious or dioecious; in the heterosporous series 

 they are dissimilar and dioecious — the ones developing from microspores bearing 

 only male reproductive organs (antheridia), and those from megaspores only 

 female organs (archegonia). Fertilization consists of the impregnation of an egg 

 cell (archegonia) by the coiled motile male cell (spermatozoid); the resulting 

 growth is the sporophyte or usually conspicuous asexual stage commonly known 

 as a fern or fern ally. 



The Pteridophyta include more than 9,000 species in about 215 genera. Although 

 world-wide in distribution, they attain their greatest number and luxuriant develop- 

 ment in the tropics and subtropics. Approximately 345 species in about 60 genera 

 are found in North America north of Mexico. 



Fam. 1. Psilotaceae Eichler Whisk Fern Family 



Terrestrial or more or less epiphytic perennial plants with short creeping 

 coralloid rhizomes; aerial stems and branches wiry, dichotomously branched, with 

 minute remote alternate scalelike leaves; sporangia somewhat depressed-globose 

 and 3-celled, opening at the apex into 2 or 3 valves, sessile in the axils of the 

 usually 2-lobed minute sporophylls on the upper part of the numerous branches; 

 spores all alike, numerous. 



A small family of two genera, Tmesipteris of Oceania and Australasia, with 

 several species, and Psilotum. 



1. Psilotum Sw. 



Characters of the family. About 3 species that are widely distributed in tropical 

 or warm temperate regions throughout the world. 



1. Psilotum nudum (L.) Beauv. Fig. 4. 



Plants dichotomously branched 3 to 5 times, usually about 25 cm. tall, rarely 

 to 5 dm. tall; common stalk simple, 3-angled, to 4 mm. thick; branches lightly 

 winged along the 3 angles; scalelike leaves about 1 mm. long; sporophylls rudi- 

 mentary. 



In swamps and low wet woods about base of trees and stumps, more or less 

 partly saprophytic, in s.e. Tex., summer; from Fla., n. to S.C, w. to Tex., 

 through Mex. and C. A. to s. S. A. and in W.I.; also widely distributed in the 

 Old World trop. 



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