| |macrosporangia, | | | |inner ones | | | |microsporangia. | | ------------+-----------+-----------------+-----------------+------- Selagniella.|Fertilized |Root, stem, leaf.|Sporangia of | |egg. |Spore-bearing |two kinds. Small| |(Develops |leaves grouped |ones contain ....|Micro- |into |on the end of | |spores. |selaginella|stem in a spike. |Large ones | |plant.) |Lower ones bear | contain ....|Macro- | |macrosporangia, | |spores. | |upper ones bear | | | |microsporangia. | | ------------+-----------+-----------------+-----------------+------- Classification of the Pteridophytes. Of the living pteridophytes four classes may be recognized. CLASS FILICINEÆ.[34] This class includes the ferns. Four orders may be recognized. =600. Order Ophioglossales.= (One Family, Ophioglossaceæ).—This order includes the grapeferns (Botrychium), so called because of the large botryoid cluster of sporangia, resembling roughly a cluster of grapes; and the adder-tongue (Ophioglossum), the sporangia being embedded in a long tongue-like outgrowth from the green leaf. Botrychium and Ophioglossum are widely distributed. The roots are fleshy, nearly destitute of root hairs, and contain an endophytic fungus, so that the roots are mycorhiza. The gametophyte is subterranean, and devoid of chlorophyll. In Botrychium virginianum, an endophytic fungus has been found in the prothallium. Another genus (Helminthostachys) with one species is limited to the East Indies. =601. Order Marattiales= (One Family, Marattiaceæ).—These are tropical ferns, with only four or five living genera (Marattia, Danæa, etc.). They resemble the typical ferns, but the sporangia are usually united, several forming a compound sporangium, or _synangium_. The Ophioglossales and Marattiales are known as eusporangiate ferns, while the following order includes the leptosporangiate ferns. =602. Order Filicales.=—This order includes the typical ferns. Eight families are recognized. _Family Osmundaceæ._—Three genera are known in this family. Osmunda has a number of species, three of which are found in the Eastern United States; the cinnamon-fern (O. cinnamomea), the royal fern (O. regalis), and Clayton’s fern (O. claytoniana). No species of this family are found on the Pacific coast. _Family Gleicheniaceæ._—These ferns are found chiefly in the tropics, and in the mountain regions of the temperate zones of South America. There are two genera, Gleichenia containing all but one of the known species. _Family Matoniaceæ._—One genus, Matonia, in the Malayan region.