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HUTCHINSON'S POPULAR BOTANY 



herbivorous wild animals. Leafless plants, however, are exceptional among 

 Phanerogams, and it is only when we descend the scale of Vegetable Life, 

 and place ourselves among the Cryptogams, or Flowerless Plants, that a 

 general absence of leaves becomes apparent. The Ferns have them, it is true, 

 their green fronds being among the chief beauties of Nature. The Mosses have 

 them also, but their minute and delicate leaves are destitute both of woody 

 vessels and stomata, and can scarcely be ranked with the busy sap-elaborating 

 organs of Flowering Plants. The Fungi are provided with nothing analogous 

 to leaves ; nor is any provision necessary, as the food on which they thrive is 

 derived from a host (plant or animal) or from decomposed organic matter 

 which does not need to be elaborated by exposure to light and air. They 



are known, therefore, as saprophytes, 

 or feeders upon rotten substances. 



A systematic description of the 

 various forms of leaves would, we 

 fear, be very wearisome. The names 

 themselves are as numerous as the 

 names of the English sovereigns from 

 Egbert to George V., and by no means 

 as easy to remember. Not only has 

 every part of a typical leaf its Latin 

 appellation, but every sort of margin, 

 base, and apex has a qualifying cog- 

 nomen. In a Grass-leaf, for example 

 (fig. 321), the flattened upper part of 

 the leaf is called the blade ; the portion 

 enfolding the stem is the sheath ; and 

 the scale-like formation between the 

 sheath and blade is the ligule. More- 

 over, the leaf is parallel-veined i.e. 

 the fibrous bundles which form the 

 skeleton run side by side without 



interlacing a characteristic feature of almost all monocotyledons ; * its 

 margin is entire i e. it is even and smooth all round and its shape is 

 linear, that is, narrow and straight and several times longer than its width. 

 The parts of a dicotyledonous leaf have an even greater number of 

 distinguishing names. Take, for instance, the compound le&f of the Dog-rose 

 (Rosa canina], the Ash (Fraxinus excelsior}. Sainfoin (Onobrychis vicicKfolia\ 

 Silver-weed (Potentilla anserina\ or Kidney Vetch (Anthyllis vulneraria). 

 The leaf as a whole is called compound because its stalk bears numerous 

 leaflets, it is pinnate (Lat. pinnatus, feathered) because leaflets grow 

 featherwise along the sides of the stalk, and it is unequally or impari- 



* There are three or four British monocotyledons notably the Black Bryony (Tamus 

 communis) and the Cuckoo-pint (Arum maculatum) which have net-veined leaves. 



FIG. 311. SWEET VIOLET (Viola odoratz). 

 An example of Involute vernation. 



