. Our native ferns and their allies [microform] : with synoptical descriptions of the American Pteridophyta north of Mexico . Ferns; Ferns; Pteridophyta; Fougères; ; . Figs. scrru Stages of growth 20 OUR NATIVE FERNS AND THEIR ALLIES. liverworts called the protliallium. Different ferns vary in the method of forming this prothallium, some producing it im- mediately at the spore and others after the formation of a thread- like growth known as the pro- embryo. The prothallium is en- /A X-V>K/CXj7V^~/0 tirely composed of cellular tissue, and in the true ferns (POLYPO- Di ACEi*:) is broadly cor
. Our native ferns and their allies [microform] : with synoptical descriptions of the American Pteridophyta north of Mexico . Ferns; Ferns; Pteridophyta; Fougères; ; . Figs. scrru Stages of growth 20 OUR NATIVE FERNS AND THEIR ALLIES. liverworts called the protliallium. Different ferns vary in the method of forming this prothallium, some producing it im- mediately at the spore and others after the formation of a thread- like growth known as the pro- embryo. The prothallium is en- /A X-V>K/CXj7V^~/0 tirely composed of cellular tissue, and in the true ferns (POLYPO- Di ACEi*:) is broadly cordate or reni- form in shape, and bears large numbers of root-hairs from the under part of its posterior portion (Figs. 12. 13). The prothallium varies in size from less than one tenth of an s. 12, 13.—Prothallium of/V?>-/j . , ^ ^\ • a c • 1 lata Linn, f., showing two mch up to onc third of an mch in its widest part. On the under surface of the prothallium two sorts of organs are produced analogous to the stamens and pistils of the Spermaphyta, respectively known as anthcridia and archcgonia. The position of these organs on the prothallium varies in different sub orders. In some species, notably the , the two kinds of sex- ual organs are produced on separate prothallia, so that the plant becomes dioecious instead of monoecious. Analogous cases are familiar to all among flowering plants like the willows, poplars, and box elders (dioecious), and begonias and melons (monoe- cious). 63. Antheridia.—These are small masses of tissue developed in the same manner as the root-hairs, consisting of a single layer of cells forming the wall, and containing a number of spirally coiled threads, usually with a number of cilia on their anterior coils. At maturity the antheridium swells by the ab- sorption of water and finally bursts its wall, discharging these coiled filaments, which possess the power of locomotion, and for this reason are called anthcrozoids. These an
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