CHAP, i.] PLANT ARCHITECTURE. 17 



Kingdom at present living on dry land has been directly 

 derived. The division of the latter into numerous groups 

 depending, and the endless variation in the properties of 

 protoplasm within certain limits as illustrated by the not 

 unfrequent occurrence of an unusual development popu- 

 larly known as a " sport/' meaning a departure from the 

 ordinary type in some minor feature, such as the colour 

 of the flower or the form of the leaf. At this stage it is 

 necessary to state that the great variety of form, colour, 

 and size presented by the various parts of plants are 

 those best suited to their requirements, and not mere 

 fanciful developments produced with no special object in 

 view, and in many instances, as the fertilization of flowers 

 by insects, not only is colour and form of importance, 

 but the various parts of the flower are so constructed 

 that certain movements take place at the proper moment 

 with machine-like accuracy. Now if the modification of 

 structure presented by a " sport " enables either the 

 vegetative or reproductive portions to do their work 

 better than by the old method, other things being equal, 

 it is not difficult to understand that the descendants of 

 the "sport," inheriting its peculiarity, will spread at a 

 greater rate than the old and superseded parent stock ; 

 thus we get the foundation for a new form or variety 

 depending on the amount of difference existing between 

 the parent form and its aberrant offspring. As the 

 above mentioned element of variation, due to unexplained 

 causes, but for that reason none the less conformable to 

 natural laws, is constantly at work, a second <( sport " 

 originating from the first will result in the production 

 of a plant still further removed from the original type in 

 structure, thus by repeated variations in vegetative 



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