134 



PHILOSOPHICAL NOTES ON 



homologous, but the former the descendants of the latter. More- 

 over, is it not enough to know that in teratologieal specimens the 

 ovule is transformed into a leaf? 



In Sargassiun, Fucus, and many other seaweeds, we see how 

 the teeth of phsenogamic leaves may have originated, without 

 going the length of supposing them inherited, as atrophied lobes, 

 of Gigartina. For in Sargassum, we have the leaf teeth already 

 altered, and therefore may have been inherited directly and tale 

 quale by the phaenogamic leaf, sujDposing it to have descended 

 from the seaweed cladophyl. It is more than probable that in 

 Sargassum vulgare (Fig. 21) and others, the teeth are merely the 

 depauperized lobes of some such ancestor as Gigartina lanceolata 

 (Fig. 16) or Lenormandia marginata (Fig. 22). 



In the latter, on the same cladophyl, we have fully develo^jed 

 branches, and also their atrophied representatives, the teeth. It 

 undoubtedly also gives us a notion of the possible origin of 



Fig. 22. Lobes, lobelets, unci teeth of Lenormandia maryinata — H. V. & 11. 

 ("Harvey's Phyc. Austr.," pi. 235). 



pin7iate leaves in pha^nogams, the midrib being a depauperized 

 l)lade of the cladophyl, and the pinmc its branches. 



Serrations or crenations on the margins of leaves are a \'ery 

 common feature indeed, in a vast number of plants of very diverse 



