Text-book of botany, morphological and physiological . s and the lower parts ofthe lamina are often completely unfolded while the apex is still growing (as inNephrolepis). This apical growth is not unfrequently interrupted periodically {videinfra) ; in Lygodium the leaf-stalk or the rachis even resembles a twining stemgrowing for a long period, the pinnae presenting the appearance of leaves. Theamount of metamorphosis of the leaves is, notwithstanding, very inconsiderable ;on the same plant the same forms of leaves, mostly foliage-leaves, are constantlyrepeated ; scale-like leaves occur on und
Text-book of botany, morphological and physiological . s and the lower parts ofthe lamina are often completely unfolded while the apex is still growing (as inNephrolepis). This apical growth is not unfrequently interrupted periodically {videinfra) ; in Lygodium the leaf-stalk or the rachis even resembles a twining stemgrowing for a long period, the pinnae presenting the appearance of leaves. Theamount of metamorphosis of the leaves is, notwithstanding, very inconsiderable ;on the same plant the same forms of leaves, mostly foliage-leaves, are constantlyrepeated ; scale-like leaves occur on underground stolons (^. g. in Struthiopierisgeniiatiica), and in many cases the fertile leaves (those which bear sporangia) assumespecial forms. Such differences as occur in most Phanerogams are not found inthe development of the leaves of one plant; Platyceriwn alcicome must, however, bementioned, as having the foliage-leaves alternately developed as broad plates closelyapplied to the -supporting surface and as long dichotomously branched ribbon-shaped. tIG. 359.—Pteris aqiiilitta, a part of the under^rouiKj stem witli leaves and bases of the leaf-stalks (reduced about one-half) ;/ older portion of the stem bearinjj the two bifurcations // and //, ss the apex of the weaker branch //; beside it theyoungest leaf-rudiment 8 ; 1-7 the leaves of this branch, one being developed in each year; 1-5 the leaves of earlier years,which have already died off at some distance from the stem ; 6 the leaf of the present year with unfolded lamina, the stalkhaving beencut off; 7 the young leaf for next year; at the apex of the stalk is the lamina still very small and entirely clothed withhairs. The leaf-stalk / bears a bud IIa, which has developed a leaf b that has already died off. The more slender filaments areroots. All the parts shown in the figure are underground. erect leaves. Amons^ the various forms of trichomes of Ferns those termed PalecBare especially striking, from their great numbers
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectbotany, bookyear1875
