i6 PLANTS i THEIR NATURAL GROWTH 



PLATE 6. 



"The great business of study is to form a mind adapted, and adequate, to all times and all occasions ; to which all Nahire 

 is then laid open, and which may be said f 6 possess the key to her inexhaustible riches."— Sir Joshua Reynolds, Discourse XI. 



The first figure on this plate is the highly ornamental leaf of the greater Knapweed 

 (Centaurea scabiosa). As the plant is represented in its natural growth at fig. 247, we shall 

 defer further comment until then ; the leaf is merely detached from want of space for it on plate 

 30, as it is one of the large lower leaves of that plant. 



Fig. 67, the leaf of the Corn Marigold (Chrysanthemum segetum), is very ornamental in 

 character ; the whole plant is well worthy of the ornamentist's consideration. Its large yellow 

 flowers render it a conspicuous object ; it is found, together with the Blue Cornflower (Centaurea 

 Cyanus) and the Scarlet Poppy (Papaver Rhceas), in the ripening wheat, and is, like those, one of 

 the characteristic plants of autumn. 



Figs. 69, 70, 71, 72, the leaves of the Ivy-leaved Speedwell (Veronica hederifolia), have 

 been already referred to in our remarks on the variation of form often seen in the leaves of the 

 same plant. 



Though the great majority of leaves are bi-symmetrical in fofm, we occasionally meet 

 with examples wanting in this symmetrical character ; the leaf of the Elm ( Ulmus campeStris) is 

 a familiar example of this. We see it still more clearly in the various species of Begonia— ^d^ in 

 fig. 68, the leaf of the B. suffruticosa, and in fig. 76, that of B. Wetoniensis. In this fa.mily the 

 difference of size between the portions on either side of the main rib is very marked indeed. In 

 speaking botanically of leaves being bi-symmetrical, we disregard any minor variations, or slight 

 deviation in the dimensions, the word being used in a general sense, and not as implying 

 geometrical accuracy : since, in almost every leaf, though practically it may be said to be bi- 

 symmetrical, small differences of form will be easily detected in comparing one half, with the other. 

 Where leaves are unsymmetrical, it will always be found that they are arranged alternately on the 

 stem : no instance is know of inequilateral leaves being arranged in an opposite manner on the 

 stem ; hence this would seem to prove, in the words of De Candolle, " That this inequality ought 

 to be referred to the position of the leaf upon the plant favouring the development of one of its 

 sides more than the other, and in this case it is always the lowest which is developed most" This 

 law is still more evident in the leaflets of pinnate leaves ; when they are unequal, as is ordinarily 

 the case, the lower part is always that most developed. We see this in the leaflets of the Knap- 

 weed, on the present plate. Figs. 152, 173, 258, are also good examples. In palmate leaves, 

 leaves of a radiate character, like those of the Horse Chestnut, when the lateral leaflets, though 

 forming part of a symmetrical whole, are not, in themselves, symmetrical, the larger portion will 

 always be on the external side — that part furthest removed from the general central line of the 

 leaf Not only do leaves, when viewed individually, present ordinarily a general symmetry of 

 form, but also a due symmetry in regard to their position on the stem in connection with other 

 leaves ; thus, with scarcely an exception, all leaves that spring from the same level are of equal 

 size : .they are, at least, normally so, though accidents of growth may have disturbed this natural 

 symmetry. We see this very clearly in the Ground Ivy ( Nepeta glechoma, fig. 153), or the 

 Meadow Crane's-bill (Geranium pratense, fig. 184). A very curious instance of this law of 

 symmetry and the due balance of parts is seen in the Ruellia anisophylla, where the leaves, though 

 growing in pairs, are not equal, one being very small and narrow as compared with the other ; 

 yet, on comparing successive pairs, the small leaf of the pair is found to occur alternately, first on 

 the left side, then on the right. In the Deadly Nightshade or Dwale (Atropa Belladona) the 

 leaves, though in pairs, are of very unequal size, one of each two being always much larger than 

 the other, as may be seen by reference to fig. 271. In fig. 339 we have a design based on this 

 curious and abnormal growth. When leaves are in whorls, or verticillate in arrangement, all the 

 leaves composing a whorl are ordinarily of the same size : occasionally, however, they vary from 

 large to small, placed alternately. 



The leaf of the Daisy ( Bdlis perennis, fig. 74) has already been referred to in speaking of 

 the various foliate forms, as an example of the spatulate type ; while the Harebell leaf (Campanula 

 rotundifolia, fig. 75) is a type of the rounded leaf. We may also cite it as a further instance of 

 the variety of leaf form to be sometimes found on one plant, as the lower leaves alone are of 

 this character, the upper ones being thin and strap-shaped. The plant as a whole is admirably 

 adapted for employment in design, its delicate growth and graceful bell-shaped flowers being 

 features of great beauty and adaptability to art-work. 



The leaves of the various species of Sarracenia are curious examples of the very abnormal 

 forms sometimes assumed. The variation of colour in these is very striking In the 6: Drum^ 

 mondii the lower portion is light green, gradually merging into pure white, and on this, as aground 



