Organography of plants, especially of the archegoniatae and spermaphyta . inst the gnawing of animals. The Dicksonieae furnish a transition tothe hair-formations of the Cyatheaceae. In them, both upon the upper andunder side, as well as upon the edge of the prothallus, there are gland-hairswhich have a basal foot-cell out of which a cell-row, sometimes branched,develops. Exceptions to the usual heart-like outline of the prothallus arefound in some epiphytic Polypodiaceae, as well as in the Vittariaceae ^ andspecies of Anogramme. These epiphytic forms have long band-like pro-thalli with no cush
Organography of plants, especially of the archegoniatae and spermaphyta . inst the gnawing of animals. The Dicksonieae furnish a transition tothe hair-formations of the Cyatheaceae. In them, both upon the upper andunder side, as well as upon the edge of the prothallus, there are gland-hairswhich have a basal foot-cell out of which a cell-row, sometimes branched,develops. Exceptions to the usual heart-like outline of the prothallus arefound in some epiphytic Polypodiaceae, as well as in the Vittariaceae ^ andspecies of Anogramme. These epiphytic forms have long band-like pro-thalli with no cushion of tissue upon the under side, and the prothallus hasmany layers only at the positions where the archegonia arise (Fig. 145).This condition may be connected with the epiphytic method of life, inas- The analogous condition is found in some heart-like prothalli of the Polypodiaceae and Aneimia,where, if an archegonium is fertilized at an early period, there is unequal development of the wingsof the prothallus, and one of them may be entirely suppressed. ^ See p. ^^s-\^ w h Fig. 144. Hemitelia (Amphicosmia) Walkerae. Development of pro-thallus. I, young prothallus ; w/t, rhizoid. 2 and 3, older prothalli, eachwith two vegetative points, f, v. Magnified ; 1 more highly so than 2 and 3. HEART-SHAPED PROTHALLI OF POLYPODIACEAE 201 much as such epiphytic prothalli evidently can only develop archegoniain special favourable conditions, and they live vegetatively between times ;
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