THEORIES OF ORGANIC EVOLUTION 



" The further development, however, goes on cease- 

 lessly in the leaf, from node to node ; its midrib is elon- 

 gated, and more or less additional ribs stretch out from 

 this towards the sides. The leaves now appear notch- 

 ed, deeply indented, or composed of several small 

 leaves, in which last case they seem to form complete 

 little branches. The date-palm furnishes a striking 

 example of such a successive transformation of the 

 simplest leaf form. A midrib is elongated through a 

 succession of several leaves, the single fan -shaped 

 leaf becomes torn and diverted, and a very com- 

 plicated leaf is developed, which rivals a branch in 

 form. 



" The transition to inflorescence takes place more or 

 less rapidly. In the latter case we usually observe that 

 the leaves of the stalk loose their different external di- 

 visions, and, on the other hand, spread out more or 

 less in their lower parts where they are attached to the 

 stalk. If the transition takes place rapidly, the stalk, 

 suddenly become thinner and more elongated since the 

 node of the last-developed leaf, shoots up and collects 

 several leaves around an axis at its end. 



" That the petals of the calyx are precisely the same 

 organs which have hitherto appeared as leaves on the 

 stalk, but now stand grouped about a common centre 

 in an often very different form, can, as it seems to me, 

 be most clearly demonstrated. Already in connection 

 with the cotyledons above, we noticed a similar work- 

 ing of nature. The first species, while they are develop- 

 ing out of the seed-kernel, display a radiate crown of 

 unmistakable needles; and in the first childhood of 

 these plants we see already indicated that force of 



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