CHAPTER XVII 



MORPHOLOGY, OR THE STUDY OF THE FORMS OF 

 PLANT MEMBERS 



220. 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 un- 

 usual members, are supposed to represent or to stand in 

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



221. 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 the 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 or modification 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. 



222. 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. 



223. 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 homol- 

 ogous. Thus the tendril, in the example assumed above, 

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



(105) 



