X Suggestions for Future Study 199 



a downward-growing axis or root, and that the young stem 

 bears on its sides one or two seed-leaves or cotyledons. 

 Here we have the simplest form of higher plant — an axis 

 with appendages. 



And when we study the various appendages which are 

 borne by the upward-growing axis or stem, we see that they 

 are all fundamentally the same. The seed-leaves are not 

 unfrequently of the same general type as the foliage-leaves ; 

 the latter are connected by gradations with the scales 

 which are wrapped round the buds, and the bracts which lie 

 at the bases of the flowers. The transition from bracts to 

 calyx may be conveniently studied in the mallow, that 

 from sepals to petals in the cactus, that from petals to 

 stamens in the water-lily or in almost any garden rose 

 (which, indeed, appears to have suggested the whole theory) 

 and that from leaves to carpels in many monstrous flowers, 

 especially the double cherry. Almost every one has seen 

 some flower or other in which all the parts had reverted to 

 the state of green leaves. 



For further corroboration of this idea that all the 

 appendages of the axis are fundamentally the same in 

 structure, or are, in a word, " homologous," we must 

 watch the development of these parts. In so doing we 

 find the theory adequately confirmed ; leaves, bracts, sepals, 

 petals, stamens, and carpels all develop as precisely 

 similar processes of cellular tissue from the sides of the 

 axis. 



This conception of the plant as an axis bearing variously 

 modified but homologous appendages, floated before the 

 eyes of Wolff and Linnaeus, was more clearly grasped by 

 the poet Goethe, was systematised by De Candolle, and has 

 since been corroborated and amplified by the progress of 

 morphology. See MORPHOLOGY {Encyclopcedia Britatinica. ) 



Morphology of Tissues. — But axis and appendages 



