MEMBERS OF THE PLANT BODY 323 



nature lead us to inquire; What is the fundamental plan of 

 structure exhibited bj^ our typical plant? and What may we 

 rightly regard as the members of such a plant-body? 



98. Morphological units. We have seen that the embryo 

 flax is a miniature plant already possessing a stem-part, 

 rudimentary leaves, and the beginning of a root. These parts 

 we recognize as representing the main divisions of the plant, 

 at least before it flowers, for we know that for many weeks 

 as the plantlct grows it simply produces more root, more 

 stem, and more leaves. If we examine minutely one of 

 the leaf-buds (Fig. 280) we find it to contain a series of 

 young leaves w^iich are smaller and smaller as we approach 

 the tip of the stem until finally they appear as mere lobes. 

 Thus we see that a leafy shoot begins as a tiny dome- 

 shaped mass of growing material, which as it elongates, be- 

 comes differentiated into (1) lateral lobes, which grow into 

 leaves, and (2) a central or axial part constituting the stem 

 which bears them. Soon in the axils of the young leaves 

 appear growing points like the cone at the tip, and each 

 of these becomes a bud which may develop into a leafy 

 branch. Since corresponding parts arise at regular intervals, 

 the whole shoot, especially as it grows older, takes the form 

 of a series of segments or equivalent divisions each consisting 

 of a leaf-part borne by a stem-section from which a bud or 

 rudimentary branch may also develop. The embryo, we 

 remember, had just these parts, and in addition bore a root. 

 Often, such a shoot-segment cut from a plant and placed 

 under favorable conditions for growth will send out a root, 

 and develop other segments much as an embryo does; and, 

 commonly, a cutting which consists of a single leaf attached 

 to a bit of stem, is the least part of a flowering plant that 

 can be made to grow independently. Hence such a seg- 

 ment consisting of an internode and its node, together with 

 the leaf or leaves it bears, has been regarded as constituting, 

 in a way, a unit of plant structure. 



99. Members of the plant body. A plant like flax is some- 

 times thought of as a colony of segments or in other words 

 as a community of closely connected individuals each con- 

 sisting of a stem-part and leaf-part, and capable of producing 



