ANGIOSPERMS. DICOTYLEDONS. 453 



floral leaves ; a few facts only can be mentioned here which are peculiar to or charac- 

 teristic of the foliage-leaves of Dicotyledons. These are usually differentiated into 

 a slender stalk (petiole) and a flat blade (lamina] which is very often branched, that 

 is, lobed, pinnated, compound or divided ; where the surface is not broken up in this 

 way, the tendency to branching is shown by indentations, teeth or notches at the 

 margin. The branching of the lamina is monopodial. The sheathing amplexicaul 

 base, such as occurs for instance in the Umbelliferae, is not common among the 

 Dicotyledons, and stipules occur more frequently in its place. Among special 

 peculiarities must be mentioned the not infrequent cohesion of opposite leaves into 

 a lamella which is pierced by the stem (connate-per foliate leaves), as in Lamium amplexi- 

 caule, Dipsacus fullonum, some species of Silphium, Lonicera Caprifolium, and some 

 species of Eucalyptus, and the extension downwards of portions of the lamina on 

 the right and left of the insertion of the leaf forming wings on the stem (Recurrent 

 leaves) in Verbascum thapsiforme, Onopordon, etc. ; the not uncommon peltate leaf is 

 scarcely found in any other class in so marked a form as in Tropaeolum, Victoria 

 regia and some other Dicotyledons. The power possessed by the Dicotyledons to 

 develope their foliage-leaves into organs with a great variety of functions in accordance 

 with varied conditions of life is shown very strikingly in the frequent occurrence of 

 leaf-tendrils and leaf -spines, and still more in the formation of the pitchers of Nepenthes, 

 Cephalotus and Sarracenia. 



The venation of all foliage leaves except the thick leaves of succulent plants is 

 distinguished by the numerous veins which project on the under surface, and by their 

 numerous curvilinear anastomoses formed by more slender vascular bundles running 

 through the mesophyll. The mid-rib, which divides the leaf usually into two symme- 

 trical, but sometimes into two unsymmetrical portions, gives off lateral veins to the 

 right and left ; and not unfrequently one, two or three stout veins start from the base 

 of the lamina right and left of the median line, and like it give off lateral veins. The 

 entire system of projecting veins in a foliage-leaf is a monopodial branch-system 

 developed in the same plane, the intervals between the branches being filled with a 

 green mesophyll, in which the anastomoses form a small-meshed network ; still 

 slenderer bundles are usually formed inside the meshes and end blindly in the meso- 

 phyll. The projecting veins are generally wanting in the scale-like or membranous 

 cataphyllary leaves, in hypsophyllary leaves and in the leaves of the floral envelopes ; 

 their venation is simpler and more like that of Monocotyledons. 



It may be shown that the scales \ which usually cover up the buds of woody 

 Dicotyledons during their resting period, are only forms of foliage-leaves arrested at 

 various stages in their development. Generally the rudiment of the lamina is only 

 slightly, while the lower part, the base of the leaf, is more strongly developed. That 

 they are only peculiar modifications of rudimentary foliage-leaves appears from the 

 fact, that the rudiments which normally become scales (bud-scales, etc.) may be made 

 by artificial means to develope into ordinary foliage-leaves. 



The flower 2 . In the great majority of Dicotyledons the parts of the flower 



1 Goebel, Beitr. z. Morphol. u. Physiol. d. Blattes (Bot. Ztg. 1880). [See also note and reference 

 to Bower's investigations on p. 314.] 



2 ' The following floral diagrams are designed partly from my own observations and partly from 

 the statements of Payer and of Doll in his Flora d. Groszherzogthum Baden. The figures placed 



