STRUCTURE.] NERVURES RIBS. 263 



a particular size or direction, as by Linnaeus and his followers. 

 Nothing is more destructive of accurate ideas in natural 

 history than giving names well understood in one kingdom of 

 nature to organs in another kingdom of a different kind, unless 

 it is the, perhaps, more reprehensible practice of giving two 

 names conveying different ideas to the same organ in the 

 same kingdom of nature. Thus, when the veins of a plant 

 are termed nerves, it is naturally understood that they 

 exercise functions of a similar nature to those of the nerves 

 of animals : if otherwise, why are they so called ? But they 

 exercise no such functions, being mere channels for the 

 transmission of nuid. Again, if one portion of the skeleton 

 of a leaf is called a vein, and another portion a nerve, this 

 apparently precise mode of speaking leads yet more strongly 

 to the belief that the structure and function of those two 

 parts are as widely different as the structure and function of 

 a vein and a nerve in the animal economy ; else why should 

 such caution be taken to distinguish them? But, in fact, 

 there is no difference whatever, except in size, between the 

 veins and nerves of a leaf. In order to obviate the incon- 

 venience of using the word nerve, the term nervure is now 

 often substituted. 



For the sake of obtaining great precision in describing 

 such a very important and various-formed organ as the leaf, 

 many terms have been invented, especially by Link and 

 De Candolle, which, although not used in daily parlance, are 

 important where brevity and precision are required. With- 

 out exactly adopting the nomenclature of either of these 

 distinguished writers, it appears that upon it a system of 

 names may be founded, to which the systematist can have 

 little to object. 



It has been usual to call that bundle of vessels only which 

 passes directly from the base to the apex of a leaf the rib, or 

 cost a, or midrib. This term should be extended to all main 

 veins proceeding directly from the base to the apex, or to the 

 points of the lobes. There is no difference in size in these 

 ribs; and in lobed leaves, which may be understood as simple 

 leaves approaching composition, each rib has its own particular 

 set of veins. 



