THE LIVING PLANT. 



31 



during which they may grow and even multiply 

 by subdivision; and a sexual stage, in which they 

 reproduce themselves by means of the conjoint 

 action of the male and female cells. 



Those chlorophyll-producing plants which have 

 anthers containing male spores (pollen) and ovules 



containing one or more female cells (oospheres; 

 are the so-called flowering plants. These are 

 vascular as well as cellular in construction, and 

 are in all ways the most highly organized of all. 

 It is with such plants that the gardener has 

 most to do, and to which, therefore, most atten 



Fig. 26.— To show contraction induced by the contact of insects. Tentacles on Leaf of Sun-dew (Drosera). 



1. Glands at the extremity of a Tentacle ; X30. 2. Leaf with all its Tentacles inflexed towards the middle. 3. Leaf with half the Tentacles 

 inflected over a captured insect. 4. Leaf with all the Tentacles extended. Figs. 2, 3, and 4X4. 



tion will be given in these pages. Flowering 

 plants have mostly well-marked roots, stems, 

 buds, leaves, and flowers, to each of which a 

 few words must be devoted. 



Sensation and Movements in Plants. 



In animals sensation is made evident by the 

 medium of nervous tissues. Plants have no 

 distinct nervous apparatus, but the protoplasm 

 of which they consist is very sensitive to im- 

 pressions of various characters. It has, as the 

 chemists say, a great affinity for water, by virtue 

 of which property it absorbs large quantities of 

 fluid, and by the alternate turgescence and 

 flaccidity which ensue the form is greatly altered. 

 Furthermore, it is contractile, the contraction 

 being influenced by light, heat, by chemical sub- 

 stances such as acids, electrical currents, and so 

 on, matters that must here be dismissed with 

 the mere mention. Nevertheless, the move- 

 ments which are witnessed in leaves, tendrils, 

 root-tips, and twining plants, in the opening 

 and closing of flowers, the growth-movements 

 of roots and of shoots generally, are all depen- 

 dent upon impressions made by various agencies 

 singly or in combination on the protoplasm. It 

 is probable that some of these movements are 

 not only dependent physically on the varying 

 amounts of turgescence in the protoplasm, but 



also on chemical changes in the constitution of 

 the fluids; thus, in so-called insectivorous plants, 

 such as Drosera (fig. 26), it is not merely the 

 mechanical stimulus of touch which causes the 

 leaf, or portions of it, to fold over the intruding 

 substance ; for if the sub- 

 stance be of a nitrogenous 

 character, as the body of 

 an insect or a fragment 

 of meat, a "ferment" is 

 formed in the protoplasm 

 which dissolves the meat 

 and ensures its absorp- 

 tion. The movements of 

 the leaves of sensitive 

 plants also are not only 

 accompanied by varia- 

 tions in the amount of 

 turgescence, but also by 

 changes in the chemical 

 constitution of the cell- 

 juices. These phenomena 

 are facilitated by the 

 passage of threads of pro- 

 toplasm from one cell to 

 another through minute 

 openings in the cell-walls (fig. 27), so that there 

 is a "continuity of protoplasm" throughout the 

 entire plant. In the expansion and closure of 

 the parts of the flower the movements appear 



Fig. 27. — The figure shows the 

 partition between the cells per- 

 forated by very minute aper- 

 tures, through which threads 

 of protoplasm pass from one 

 cell to the other. To see these 

 phenomena the tissues require 

 to be stained and examined 

 under a high power of the 

 microscope. 



