192 LETTER XLV. 



several cases, where the structure peculiar to one class 

 assimilates itself to that of the other. 



A case of this sort, where Aristolochias themselves 

 may be considered as t\^ified among Endogens, occurs 

 in the Arum Tribe {Plate XLVI. 2.). You probably 

 know this tribe already, from the common spotted 

 Arum (A. maculatum) of our hedges, or the speckled 

 Dragon Arum (A. Dracunculus) of the gardens. 

 These two species, at least, are so very common, that 

 if you do not yet know them, you can have no difficulty 

 in procuring them for examination. 



The Arum Tribe consists of stemless or long-stem- 

 med plants, whose internal structure is strictly that of 

 Endogens, but whose leaves bear more resemblance to 

 those of Exogens ; it is, however, to be observed, that 

 the lobed figure of the leaves, and their branched 

 veining, to which the resemblance is due, need not 

 be confounded with the netted veining of Exogens, be- 

 cause in Arum, the veins are branched rather than 

 netted, and arc in a great measure destitute of the 

 lateral, minute branchlets, to which the peculiar ap- 

 pearance of Exogenous leaves is chiefly owing. Many 

 of these have large, tuberous, under-ground stems, 

 which, although acrid, and even poisonous when raw, 

 nevertheless, by slicing, washing, and cooking, become 

 fit for food, and are actually so employed, in England 

 only in a few places, or in times of scarcity, but in 

 tropical countries, as a common, every-day, esculent 

 vegetable. Their foliage is generally more or less 

 lobed, and sometimes very curiously, but is so much 



