File:The natural history of plants, their forms, growth, reproduction, and distribution; (1902) (14783488895).jpg

Identifier: naturalhistoryof01kern (find matches)
Title: The natural history of plants, their forms, growth, reproduction, and distribution;
Year: 1902 (1900s)
Authors: Kerner von Marilaun, Anton, 1831-1898 Oliver, Francis Wall, 1864- Macdonald, Mary Frances Ewart Busk, Marian Balfour, Lady
Subjects: Botany
Publisher: London, Blackie
Contributing Library: NCSU Libraries
Digitizing Sponsor: NCSU Libraries

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
h foliage-leaf is divided by a midrib, running from the apexto the leaf-stalk, into two similar or almost similar halves, in the begonias, manyclimbing figs, in Celtis occidentalis, elms, and numerous other plants, the two RELATION BETWEEN POSITION AND FORM OF GREEN LEAVES. 421 portions of the leaf separated by the midrib are very unlike. The dissimilarity isseen principally at the base of the leaf—it looks as if a piece had been taken outof one side, or as if the leaf had there been cut off obliquely (see fig. 110). Thecorrect explanation of this want of symmetry will perhaps be arrived at mosteasily by supposing the suppressed portion to be completed, or in other words,let us suppose the smaller half to be just as large and well-developed as theother. It is then evident that the added portions would be covered over by theneighbouring leaves, and consequently they would be deprived of light, and thatin these parts, therefore, the chlorophyll-bodies, if present, would not be able to
Text Appearing After Image:
iig. 111.—Mosaic of of unequal size. 1 Projecting branch of Deadly Nightshade (Atropa Belladonna) looked at from ( seen from above. B. 8 Selaginella Helvetica, carry on their activity. These portions of the foliage-leaves would accordinglybe superfluous, and it is foreign to the ways of plants to manufacture so muchleaf-tissue for no purpose whatever. Plants never form anything which issuperfluous and useless; in the construction of all the organs the principleapparently is to attain the greatest possible result with the least amount ofmaterial, and to utilize the given conditions, above all, the existing space, as far aspossible. Yet another phenomenon, viz. the unequal size of adjoining leaves on the sameplant, must be considered from this point of view. It must strike everyone wholooks down upon a horizontally-projecting branch of the Deadly Nightshade(Atropa Belladonna, see fig. Ill ^), that larger and smaller leaves are here arrangedin quite a peculiar manner. The larger leaves

Note About Images