Neilgherry Plants. 149 



most part pretty nearly natural, aided by the convenient practical 

 grouping now in use, serves all the purposes of a more strictly cor- 

 rect and philosophical arrangement, leaving us for the time, very in- 

 dependent of a better, and allowing us to proceed at our own pace, 

 leisurely feeling our way, while searching for the long and ardently 

 desired natural one. And it is in the hope that some of the readers 

 of this exposition of what is wanted, towards the construction of the 

 basement of the natural system of plants, may be induced to turn 

 their attention to the subject, and perhaps that some one luckier 

 than the rest, may stumble on a clue which will lead himself or 

 others to the desiderated point, and enable him, by the formation of 

 truly natural secondary groups or circles, to complete at least the 

 lower tier of the edifice. 



It only now remains for me to offer a few remarks on vegetable 

 organization, with reference to its employment in the construction of 

 a natural system of Botany. These must unavoidably be brief and 

 imperfect, and probably, so far as they go, little to the point, the 

 ideas of botanists on this obscure subject being far from precise or 

 settled on a firm basis, especially in what relates to the comparative 

 value which should be assigned to each part, engaged in the com- 

 plex organization of an Exogenous plant. 



The organ principally regarded as the basis of all our attempts to 

 obtain a natural arrangement is the embryo, when present, taken in 

 connection with the plant which springs from it, whether, in short, 

 it is mono-or di-cotyledonous, giving origin to an Endogenous or 

 Exogenous plant, or is altogether absent as in Acrogens ; plants still 

 further distinguished from those of the two higher groups by their 

 cellular texture, and the nearly total absence of vascular tissue. 



Dicotyledonous or Exogenous plants have a woody stem, varying 

 in solidity with their age from the tender herbaceous annual up to 

 the almost stony hardness of the iron-wood tree ; increasing, with 

 some exceptions, in thickness by the annual addition to the surface, 

 layer upon layer, of new wood, forming rings or zones round the 

 axis : these zones are intersected transversely by medullary rays 

 radiating from the central pith. Occasionally, as above hinted, in- 

 crease of thickness does not take place by means of annual zones, the 

 wood, at whatever age, appearing to consist of a single homogeneous 

 zone. Dr. Lindley has taken advantage of this circumstance, and 

 brought together most of the families in which it occurs to form his 

 group of Homogens, distinguished by the Endogenous structure of 



