. An introduction to vegetable physiology. Plant physiology. 342 VEGETABLE PHYSIOLOGY freely by their whole surface. They have, therefore, no need of differentiated absorbing or conducting tissues, which are consequently not developed. A further consequence of the ease with which they obtain their food is the readiness with which vegetative and asexual reproduction is brought about; hence sexuality is in many cases non-existent among them. Phanerogams which are completely parasitic show a similar degradation of structure. They possess no chloro- plasts, their leaves are absent or reduced to th
. An introduction to vegetable physiology. Plant physiology. 342 VEGETABLE PHYSIOLOGY freely by their whole surface. They have, therefore, no need of differentiated absorbing or conducting tissues, which are consequently not developed. A further consequence of the ease with which they obtain their food is the readiness with which vegetative and asexual reproduction is brought about; hence sexuality is in many cases non-existent among them. Phanerogams which are completely parasitic show a similar degradation of structure. They possess no chloro- plasts, their leaves are absent or reduced to the condition of scales, while their stems are often thick and Pio. 146.—Thesium alpinum. Piece or a boot with suckeb in section, x 85. (After Kernel-.) Their roots are replaced by the so-called haustoria, which penetrate into the tissues of their hosts, complete fusion of the tissue of the host and the parasite frequently taking place. We have representatives of such parasites in the British flora in Cuscuta and the Orobanchacece. Many of the plants belonging to the Santalacece and the ScrophulariacecB show a partial parasitism of this kind. They have short stems which bear green functional leaves, but are peculiar in that their roots become attached by curious sucker-like bodies to the roots of other plants growing near them (figs. 145, 146), and from these suckers. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Green, J. Reynolds (Joseph Reynolds), 1848-1914. Philadelphia, P. Blakiston
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