CHARACTERISTIC FORMS OF LEAVES AND SHOOTS. ZlJ 
are characterised by the preponderance of the axial mass with a very small amount 
of leaves, the latter, on the contrary, by the preponderance of leaves closely packed 
round a short stem. If the lower parts of a plant produce slender lateral shoots 
with small scales growing upon or beneath the earth, and after rooting at a con- 
siderable distance from the mother-stock produce foliage-shoots or shoots stronger 
than themselves, they are called sfolons, as, for instance, in JSgopodium Podagraria, 
Fragaria, Struthiopteris germanica, and in Mniwn and Catharinea among Mosses. 
The greatest degree of variation from the ordinary forms of shoots is displayed 
by the flat leaf-like axes and branch-systems, and by the stem-tendrils and spiny 
shoots which occur frequently in Angiosperms. Leaf-like axes {phylloclades) 
are found in those Phanerogams in which large green foliage-leaves are wanting, 
and they replace them physiologically; their axial structure is of considerable 
superficial extent, and they produce and expose to the light large quantities of 
chlorophyll ; they generally bear only very small membranous scale-leaves. Ex- 
amples may be found in Phyllocladus among Conifers, Ruscus among Mono- 
cotyledons, and among Dicotyledons in Miihlenheckia platyclada (Polygonaceae), 
Xylophylla (Euphorbiaceae), Carmichaelia (Papilionaceae), and in Opuntia hrasiliensis 
and Rhipsalis crispaia (Cactaceai), &c. 
Stem-tendrils, like leaf-tendrils, are long, slender, filiform structures, which have 
the power of winding spirally round slender bodies in a horizontal or oblique position 
with which they come laterally into contact, and thus serve as climbing organs \ they 
spring laterally from shoots which have not the form of tendrils, and are distinguished 
by the absence of foliage-leaves, their power of forming leaves being mostly limited 
to very minute membranous scales. They are usually easily distinguished from leaf- 
tendrils by their origin, position, and by the production of leaves ; cases, however, 
occur where the morphological nature of a tendril is doubtful, as, for instance, 
in Cucurbitacese ^ Evident examples of stem-tendrils are to be met with in 
Vilis, Ampelopsis, and Passiflora. Shoots which bear strongly developed foliage- 
leaves on long slender internodes, and which have the power of winding in an 
ascending manner round upright supports, are not considered tendrils, but are 
called twining or climbing stems'^; a distinction is drawn between tendril- 
climbers (as Vitis) and stem-climbers (as Phaseolus, Hwjiulus, Convolvulus, &c.). In 
Cuscuta, where the primary shoot and all the lateral shoots, except the inflorescences, 
twine in the manner of tendrils and of climbing stems, and where foliage-leaves are 
also entirely suppressed, the peculiarities of tendrils and of climbing stems are to a 
certain extent united. A distinction similar to that between stem-tendrils and cKmb- 
ing stems is also possible in leaves; the foliage-leaves of Lygodium exhibit con- 
tinuous growth in length, and behave completely like climbing stems, the rachis 
of the leaf corresponding to a climbing axis, and the leaflets to its foliage-leaves ^ 
The axial shoots of many Angiosperms have, like the leaves, the power of 
^ According to Warming these are also metamorphosed branches. 
^ Compare H. von Mohl, Ueber den Bau und das Winden der Ranken und Schlingpflanzen. 
Tübingen 1827, [See also Darwin, On the Movements and Habits of Climbing Plants, London 
1875.] 
^ Compare Book II, Ferns, and Book III, on the Physiological Signification of Tendrils and 
Climbing Stems. 
