138 LETTER X. 



seen in gardens, although they are common enough 

 in tropical countries. It differs obviously from the 

 Protea tribe in the stamens being hypogjTious ; from 

 the Amaranth tribe in the calyx being all in one 

 piece ; and from both in the singular circumstance of 

 the lower part of the calyx becoming hardened and 

 forming a sort of spurious shell to the fruit. This 

 last is the essential character of the Marvel of Peru 

 tribe, or Nyctaginese ; which I only introduce to you as 

 a striking instance, firstly, of the highly coloured 

 condition often assumed by the calyx, and secondly, of 

 the singular manner in which one part is occasionally 

 employed by nature to perform the part of another. 



Very different from these, although also belonging 

 to the Apetalous division of Dicotyledonous plants, is 

 that most interesting natural order, which includes 

 the Oak, and the Sweet Chesnut, the Beech, the 

 Hornbeam, and the Hazel ; in short, the larger part 

 of our common European trees. In consequence of 

 its containing the Oak it bears the name of the Oak 

 tribe. Until I shall have explained to you the real 

 origin of all the parts you find in these plants, and 

 the singular manner in which they change between 

 the infancy of their flowers, and their old age, you 

 will have had but a feeble idea of the wonderful 

 power the parts of plants possess of assuming un- 

 usual forms after they have been once developed. If 

 it be true that flowers are generally seen in a mas- 

 querade dress, as some Botanists poetically assert, it 

 certainly is here that their disguise is the most im- 

 penetrable. 



