362 PHILOSOPHICAL NOTKS ON 



represent the same thing, that is, branches of leaves. When 

 atrophy has been carried further, so as to produce extinction of 

 the teeth, we have what is called an entire leaf, that is a leaf 

 without teeth. 



It necessarily follows that the angles between the teeth, Avliere 

 these do exist, represent axilltB of leaves, each having a suppressed 

 axillary bud. In Bryo2)hyUum and some ferns, however, the 

 teeth axilla? redevelop their buds. It is significant that in many 

 leaves a vein goes, not only to the tooth, but to its axilla, indi- 

 cating thereby that both the tooth and its axilla wtn-e originally 

 important organs, but now atrophied. 



Fifth. — That the petiole was originally the mi<lril) of the whole 

 leaf, with a blade on each side of it ; that a portion of the midrib 

 got rid of the blades or wings, and became a naked petiole. Most 

 naked petioles have still the remnants of the two wings in a pair 

 of ridges, on the up[)er side of the petiole. 



Sixth. — That stipules may be regarded either as — 

 (a.) Bud-scales of the leaf, and, therefore, of its sub-di\'isiou, 



Xhe axillary bud ; or 

 (h.) As portions of the petiole wings left attache<l to the stem 



when the petiole became naked. 

 In Nigella damascena it is impossil»le to say whether these 

 aj)pendages are stipules or sub-divisions of the leaf. 



Seventh. ^-'']^\vAi the cladophyl cannot be regarded as a feature of 

 certain plants only, but as u universal feature, from seaweeds, which 

 ai-e nothing but cladophyls, up to the highest plants, however 

 modified tlu'ir stem and leaf may be. 'i'lic higher plants liavr been 

 derived from seaweeds, and what we call stem and Icaxes in those 

 are only midrib and wings in these, that is cladophyls, or stem- 

 leaves. From this it follows that the midrib of a j>iniiate leaf is 

 only a conti-acted cladophyl, and its pinna' homologous with the 

 lobes of T.enormandiamar(/inafa* 



It follows also that stij^'ls an<l stipt-llar glan<ls corresijond to 

 teeth or atrophied pinnfe. Phyllocactus grand is ^\\Qi^ us a good 



