402 



MEMOIRS OF THE AMERICAN ACADEMY. 



stem, and not in their outward relations, which require exposure, expansion, and 

 elbow-room. The apparently inconsistent means of these two ends are both 

 realized, however, without interference, in the actual cycles of natural arrange- 

 ments. Through the simplicity of these cycles leaves, not very remote on the 



stem, 



are brought nearer to each 



ther. 



d into more direct internal connec- 



tion than they would have but for this simplicity 



while 



m 



th 



more prevalent 



natural forms of 



<9 



leaves, th 



are 



arest to each other on the stem 



separated as widely as is possible und 



th 



condition. That th 



pr 



is 



due 



to selection, through the utility already considered, has been shown to be 



sufficiently probabl 



I 



prop 



now to connect the prevalenc 



of 



the 

 oth 



plicity 



ycl 



with another utility. L 



that are successive, or nearest each 



on the stem, may 



be regarded 



as 



and as rend 



o 



each oth 



service. Those 

 one on the oth 



that 



are mor 



remote may come into relations of dependen 



Between th 



leaf 



d the stem the relations of nutrition 



are 



recip 



ocal. At first, and for the development of the leaf, the stern furnishes 

 nutriment to it. Afterwards the leaf furnishes nutriment for the further lateral 



exp 

 whil 



of th 



stem. 



The development of the stem itself, fir 



the leaves are 



and 



st in length, 

 and afterwards in breadth and firmness through 



th 



the nutrition afforded by the developed leaves, In 

 presume, the use or function, of a still more in 

 leaves than that we have considered. We have hither 



effect, and, we mav 



the distribution effected 

 the stem. 



the character of the d 



portant distribution of the 



:o attended only to 



\ * 



of leaves 



und 



nodes of the stem 



Their distribution along the stem, or their separation by the inter- 



least 

 and 



a still more direct and effective mode of 



one of 



plishing at 



of the property of distribution, namely, exposur 



; to light 

 The special accomplishment of this important end in the higher plants 

 secured by two different means ; by the firm fibrous structure and the breadth of 

 mis, branches, and trunks in grasses, shrubs, and trees, and by the climbing powers 

 d prehensile apparatus of climbing plants ; and in the latter we find the highest 



The d istribution 



degree of specialization or development in the vegetable world. 



effected by the separation of leaves along the stem in great measure supersedes 



the value of their distribution around 



concerned, and independently of t 



far 



the ultimate functions of 



are 



developmen 



the bud 

 and this gives freer play to the means of securing whatever advantage there may 

 be in the simpler cyclic arrangements, like the I and 



find 



lystems. Accordingly we 



gener 



pier cycles on the stems of those 



that have the 



