Text-book of botany, morphological and physiological . differentiated plants. But even in Algae the thallus is often fixed toits substratum by organs of attachment which may be compared with roots in theirhabit and in many functional properties, not only in the case of the large Fucaceae andLaminariae, but also in the unicellular Vaucheria and Caulerpa. In reference to the confirmation of the Theory of Descent brought forward at theconclusion of this work, it is of great importance to know that members differing to thegreatest extent morphologically and physiologically are connected by transit
Text-book of botany, morphological and physiological . differentiated plants. But even in Algae the thallus is often fixed toits substratum by organs of attachment which may be compared with roots in theirhabit and in many functional properties, not only in the case of the large Fucaceae andLaminariae, but also in the unicellular Vaucheria and Caulerpa. In reference to the confirmation of the Theory of Descent brought forward at theconclusion of this work, it is of great importance to know that members differing to thegreatest extent morphologically and physiologically are connected by transitional forms,and that, especially in the branched thallomes of Algae, starting points are to be found forall the differentiations of the higher plants. Distinctions which, in the ramifications ofthe Alga-thallus, are only of a weak, undefined, and rudimentary character, increase moreand more in the higher plants; points which can be sharply defined in the latter becomeindistinguishable when we are considering the more simple Thallophytes. The more L 2. FIG Ifrom the^ s bundl 17. —Part of a transverse section of the primary root oiZca Mais not farapex ; e epidermis with its strongly swollen outer walls vd; p the cortex ;; sheath ; m the pith ; a-the thickening ring in whicli lie the vessels i^^. 148 EXTERNAL CONFORMATION OF PLANTS. the attempt is made to set up sharply defined ideas for single forms, the more does onebecome convinced that all definition, all limitation, is arbitrary, and that Nature presentsgradual transitions from the indistinguishable step by step to the distinct, and finally tothe opposite. Sect. 24. Various Origin of Equivalent Members ^—(i) The differentmembers of a plant spring out of one another; the member produced may there-fore be similar (homogeneous), or dissimilar (heterogeneous) to the member whichproduces them. In the former case the formation of new members is ordinarilytermed Branching. A root, for instance, branches in the production of new
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectbotany, bookyear1875
