Plant-life, with 74 full-page illus., 24 being from photos, by the author and 50 in colour from drawings . sa). A spine, strictly speaking, is a leaf, or part of a leaf,modified on account of disturbances in nutrition. Thespines of the leaf of the Holly (Ilex) are the sharplypointed ends of leaf-veins. The Gorse, or Furze, is mostefiectively protected by a complete armoury of brancheswhich have been modified into thorns, and leaves thatare aborted into spines. Prickles are outgrowths of the epidermis and thetissue immediately beneath it; they may be regardedas hairs, many-celled, and of larger
Plant-life, with 74 full-page illus., 24 being from photos, by the author and 50 in colour from drawings . sa). A spine, strictly speaking, is a leaf, or part of a leaf,modified on account of disturbances in nutrition. Thespines of the leaf of the Holly (Ilex) are the sharplypointed ends of leaf-veins. The Gorse, or Furze, is mostefiectively protected by a complete armoury of brancheswhich have been modified into thorns, and leaves thatare aborted into spines. Prickles are outgrowths of the epidermis and thetissue immediately beneath it; they may be regardedas hairs, many-celled, and of larger growth. They areusually quite easily detached without tearing or seriouslyimpairing the epidermis. The principal use of theprickles of Roses and Brambles is in climbing, but theyalso serve to ward ofE animals. The Scotch or BurnetRose (Rosa spinosissima, Plate LXX.), which does notoften grow more than a foot high, and occupies dry,bushy places, heaths, and sandy sea-coasts, simplybristles with prickles of varying length. These pricklesare not suited for climbing, nor does the plant attempt Plate or SCOTCH ROSE {Rosa sfinonaima).Order ROSACE^^. DEFENCES OF PL^^TS 345 to climb ; they stand out nearly at right-angles to stemsand branches, and are not hooked. Doubtless, in con-sideration of the open situations in which the ScotchRose grows, and the possible attentions of browsinganimals, it needs all its warlike, threatening prickles. We must not allow our imagination to run riot inregard to these so effectively armed plants. We might,in the exercise of mere fancy, come to the conclusionthat thorns, spines, and prickles have been deliberatelyevolved as - a determined protection against animals,but the facts do not justify us in so doing. Take, forexample, the two varieties of the Common Rest-Harrow(Ononis); one grows in exposed places, in the haunts ofbrowsing animals, and is armed with spines; the otherhas few, if any, spines, and grows where thieves do notbr
Size: 1290px × 1937px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1915
