. PHYTOMERS 



7 



a plant body growing independently and 

 separately from that from which it was 

 derived. The question has been raised as 

 to when the new plant becomes an indi- 

 vidual, or whether it does so at all. Their 

 conduct after separation shows clearly 

 that they previously possessed perfectly 

 independent powers of support. If an in- 

 dividual after separation, why not before, 



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and why is not each phytomer upon the 

 plant an individual? If, upon the other 

 hand, it be considered that even separa- 

 tion does not involve individuality, then 

 the vast number of propagated plants 

 which may result from an original seed 

 must constitute but a single individual. 



Various other modes of stem propaga- 

 tion may here be referred to, and it may 

 be remarked that the process is not con- 

 fined to the node, occurring in exceptional 

 cases from fragments of the intemode, 

 root, or even leaves. The phytomers, in- 

 stead of remaining attached during the 

 rooting process (Layering) may be first 

 separated (Propagating by Cuttings). Th« 



cutting, then called a Scion, may be in- 

 serted (grafting) or a bud may be so in- 

 serted (Budding) under the bark of a liv- 



inc: stem, or may be caused to take root 

 in the soil- Propagation by tubers or 

 parts of them, as in the case of the potato, 

 is identical. It may be remarked in pass- 

 ing, that in the seed itself nature resorts 

 to a similar method, for the contained 

 embryo consists of one or more phytomers. 

 Roughly stated, the phytomer may be 

 said to consist of three portions: (1) a 

 framework consisting of strands of con- 

 ducting vessels and commonly of fibres; 

 (2) between and around the last a quan- 

 tity of soft, non-fibrous tissue; (3) a cover- 

 ing, membranaceous when young and 

 changing greatly with age. All these 

 parts are extended into the leaf, the first 

 existing in a system of branching ribs or 

 veins, the second as a filling in the meshes 

 of the former, and the third as a highly 

 developed epidermis. Morphologically 

 considered, the typical leaf (Fig. 3) con- 

 sists of three parts which, like those of 

 the stem, will be considered in detail here- 

 after* The Base (a) bears the Pulvinus 



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or organ of attachment to the stem, and 

 upon either side a membranous expansion 

 (b) called the Stipule. The stem of the 

 leaf (c) is called the Petiole. The blade 

 (d) is called the Lamina. In some plants 

 an additional organ, the Ligule, develops 

 as an appendage upon the face. 



If we could observe the phytomers of 

 such a twig during the process of forma- 

 tion in the bud (Fig. 4) we should find 

 them in a more and more rudimentary 

 condition toward its apex or centre until 

 we reached an ultimate growing point (a), 

 where development had not yet mani- 

 fested itself. Yet this point would pos- 

 sess the power, under proper conditions, 

 of continuing indefinitely the process of 

 development and growth of phytomers. 

 It therefore may be said to represent a 

 certain amount of vital energy or potential 

 growth, though by this it is not meant 

 that such energy is actually stored there. 

 Now, our fundamental ideas of flower 

 structure rest upon the fact that this vital 

 energy or potential growth may be di- 

 verted from the production of phytomers 

 and leaves such as we have been consider- 

 ing and may produce in their stead other 

 structures in which resemblance to and 



