1208 



FERNS 



FERNS 



1485. Prothallus of a 

 fern, with a young leaf 

 arising. 



and others, have recognized a much greater number of 

 genera, ranging from 150 to 250, or even more. In 

 the very unequal treatment by Diels in Die Natiir- 

 lichen Pflanzenfamilien (Engler & Prantl), some 120 

 genera are recognized. A somewhat similar differ- 

 ence prevails in regard to the number of species. 

 The Synopsis Filicum of Hooker 

 and Baker (1874), supplemented 

 by Baker's New Ferns (1892), 

 recognizes some 2,700 species. 

 It is the too prevailing tendency 

 in this work (1) to fail to recog- 

 nize many valid species which 

 have been described by German 

 and French botanists, and (2) 

 to mass under one name very 

 diverse groups of species from 

 distant quarters of the world 

 from 8 to 10 species not infre- 

 quently appearing as a single 

 so-called "variable species." The 

 most recent book dealing with the 

 whole order of ferns, the Index 

 Filicium by Carl Christensen, 

 recognizes approximately 150 

 genera and 6,000 species, and this 

 number is continually increased 

 as the result of further tropical 

 exploration and more careful 

 study. New forms are constantly coming in from the 

 less-explored parts of the world, and within the last few 

 years several new species have been described from the 

 United States, including some from the better-known 

 parts. Of this number some 200 species are in occa- 

 sional cultivation in America, but the species that 

 form the bulk of the fern trade do not exceed two 

 dozen. In Europe several hundred species have long 

 been in cultivation. Most of the species thrive best 

 in the mountain regions of the tropics, the mountains 

 of Jamaica and Java having nearly 600 species each, 

 and the Andes also a large number. About 165 species 

 are native in the temperate United States, representing 

 some thirty-five genera; our native species are so widely 

 distributed that usually not more than twenty-five to 

 fifty will be found within the limits of one state, and 

 the common species of the best locality do not number 

 more than twenty. Recent explorations in southern 

 Florida have discovered in that state the presence of a 

 considerable number of West Indian species not found 

 elsewhere in the United States. 



The ferns are commonly classified as part of a group 

 of spore-bearing plants, with vascular (woody) tissue 

 in stem and leaves; this group is technically known as 

 the Pteridophytes, and is ordinarily divided into three 

 orders; viz., the Equisetales, including the horsetails 

 and scouring rushes; the Lycopodiales, including the 

 selaginellas and the club mosses, or ground pines; and 

 the Filicales, including the true ferns and their nearer 

 allies (see pp. 7-9, Vol. I) . The Lycopodiales and Equi- 

 setales are really not as closely related to ferns as this 

 grouping would indicate. 



It should be noted that neither the family nor the 

 generic limitations are in a settled condition. The 

 researches of Bower, Lang, Jeffrey, and others have 

 resulted in some changes of classification which are 

 not included below because they are not complete 

 enough. Their conclusions are undoubtedly correct 

 but are not at present usable. 



The families of the order Filicales may be distin- 

 guished as follows: 



A. Spores of one sort. (Isosporous.) 



B. Sporangia fleshy, with no ring, rising from the interior 



tissues of the If. (Eusporangiate ferns.) 



1. Ophioglossaceae. ADDER'S-TONGUE FERNS. Her- 

 baceous small ferns with the sporangia borne in spikes 



or panicles on highly modified divisions of the large 

 fleshy foliage Ivs.; prothallium tuberous, subterranean, 

 without chlorophyll. 



2. Marattlaceas. Coarse ferns with large fleshy 

 sporangia on the under surface of the If., arranged in 

 circular or boat-shaped receptacles; prothallium above 

 ground, green. 



BB. Sporangia rising from an epidermal cell, with an 

 elastic ring of peculiar cells, which assist in scat- 

 tering the spores by rupturing. (Leptosporangiate 

 ferns). 



c. Lvs. filmy, usually only 1 cell thick between the veins. 



3. Hymenophyllaceae. FILMY FERNS. Sporangia 

 attached to a thread-like receptacle arising in a cup at 

 the end of the If. : ring complete, horizontal or oblique. 



cc. Lvs. herbaceous or leathery. 



D. Ring incomplete or rudimentary: sporangia in 



panicles. 



4. Osmundaceae. FLOWERING FERNS. Coarse swamp 

 ferns developing copious green spores early in the 

 season: sporangia in panicles at the apex or middle of 

 the If. or on separate Ivs. 



DD. Ring apical: sporangia usually single under a scale, 

 or in panicles. 



5. Schizaeaceae. Upright or climbing ferns with 

 ovate sporangia, which open vertically. 



DDD. Sporangia sessile, either single or in 

 clusters of 3-6. 



6. Gleicheniaceae. Terrestrial 

 ferns with Ivs. of firm texture and 

 usually of indetermi- 

 nate growth: sporangia 



opening vertically, in 

 clusters of 3-6. 



7. Ceratopteridaceae. 

 Aquatic ferns with 

 succulent foliage: 

 sporangia very 

 large, scattered, 

 with a broad ring: 

 Ivs. of 2 sorts, the 

 sterile usually float- 

 ing. 



I486. An example of a fern hybrid. Dryopteris 



cristata X D. marginalis. 



