CHAPTER XV 



MORPHOLOGY, OR THE STUDY OF THE FORMS OF 

 PLANT MEMBERS 



208. Botanists interpret all parts of the plant in terms 

 of root, stem, and leaf. That is, the various parts, as 

 thorns, flowers, fruits, bud-scales, tendrils, and abnormal 

 or unusual members, are supposed to represent or to stand 

 in the place of roots, stems (branches), or leaves. 



209. The forms of the parts of plants are interesting, 

 therefore, in three ways: (1) merely as forms, which may 

 be named and described; (2) their relation to function, or 

 how they enable ttie part better to live and work; (3) their 

 origin, as to how they came to be and whether they have 

 been produced by the transformation of other parts. The 

 whole study of forms is known as morphology (literally, 

 the "science of forms"). We may consider examples in 

 the study of morphology. 



210. It is customary to say that the various parts of 

 plants are transformed or modified root, stem, or leaf, but 

 the words transformation and modification are not used in 

 the literal sense. It is meant that the given part, as a tendril, 

 may occupy the place of or represent a leaf. It was not 

 first a leaf and then a tendril: the part develops into a ten- 

 dril instead of into a leaf: it stands where a leaf normally 

 might have stood: it is the historical descendant of the leaf. 



211. It is better to say that parts which have similar 

 origins, which arise from the same fundamental type, or 

 which are of close genealogical relationship, are homolo- 

 gous. Thus the tendril, in the instance assumed above, 

 is homologous with a leaf. Parts which have similar func- 



(101) 



