BOTANICAL SUBJECTS. 131 



the leaf-blade. The ridges of this Eucalyptus stem I take to be 

 remnants of stem-Avings, inherited from the cladophyls of seaweeds. 



As the Eucalyptus glohulus grows older, instead of opposite 

 leaves, it gets alternate phyllodes, which we have seen are nothing 

 but cladophyls. 



The Centaurea the reader may, perhaps, not consider a good 

 example of cladophvlly, and for this reason. Let ns suppose the 

 stem to be undeveloped, that is, like a closed telescope, and the 

 leaves, with a slightly decurrent lamina, crowded together. It 

 might follow that as the stem lengthened the decurrent part of the 

 lamina would remain attached and stretched out with the stem, 

 and thus become a pair of wings. That would l)e no proof that 

 the leaf received its lamina from the stem. 



The cladophyl of the Ruscus, one might also say, is evidently 

 a branch in the axilla of the abortive leaf. The phyllode of the 

 Acacia is evidently only a part of the leaf. 



No such objection could, however, be made to the phyllode 

 of the Eucalyptus glohulus. Here we have an ordinary horizontal 

 leaf, without petiole, and with slightly decurrent margins, turning, 

 further up, into a perpendicular phyllode with a long petiole, 

 having a bud or branch in its axilla. 



Apart from all this, which I admit is not very clear, when we 

 once admit that the leaf is a branch, and a cladophyl can be 

 substituted for a branch, it would be absurd to contend that the 

 pha^nogam leaf is not the homologue of the cryptogamic 

 cladophyl. 



Many of the compositor have the petiole furnished with wings, 

 which are a continuation of the blade, or as they would be called, 

 apetiolate leaves. Indeed, a very large number of plants, although 

 they have a marked petiole, have two more or less prominent 

 ridges on its upper aspect, such as in horse-radish, beet, &c. 

 These ridges are nothing l)ut remnants of ancestral petiole-ivings, 

 continued into the blade, indicative of their cladophyl origin. 



The young pear-leaf has glandular teeth on its margin, and 

 also along the sides of its naked petiole, though here they are 

 not so plentiful. This shows that originally the pear petiole had 

 wings also, which are now aborted, the minute teeth only 

 remaining. These are sparsely placed, because the petiole, in 

 lengthening, has stretched the spaces between the teeth. Wherever 

 we look, we find that facts tend to the conclusion that the stem 



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