78 DICOTYLEDONE^. 



eating tobacco, the pungent capsicum, and the useful 

 potato are all associated here. In no other order 

 are opposite and extreme qualities so closely allied, 

 nor is diversity of constitutional structure more 

 apparent. The Solatium tuberosum may be noticed, 

 not because of its great value as an article of food, 

 but for its uncommon powers of reproduction. Besides 

 seed, it produces tuberous progeny on the stem as 

 well as in the ground. Some dwarf varieties which 

 yield numerous and early tubers, are often barren of 

 flowers and seed ; but which they may be made to 

 produce, if they be robbed of their tubers, as soon as 

 they are formed. And if the flowers be picked off 

 fhe free flowering sorts, their tubers will be increased 

 in size and numbers. Both these facts were discovered 

 by T. A. Knight, Esq., P. H. S., and are striking 

 proofs of the connexion there is between the ovipa- 

 rous and viviparous principles of the plant, or 

 rather the power each has of neutralising the 

 other, as has been before alhided to in the case of 

 bulbs. 



Passing over several orders we stop to notice Con- 

 volvulacece ; among which we find the very useful 

 tropical plant Ipomcea batatas, which yields, when 

 properly cultivated, tubers of a far larger size, and 

 nearly equal in value to those of the potato. The 

 leafless Cuscuta is also ranked here, a most remark- 

 able vegetable parasite ; its proper roots are only useful 

 during the infancy of the plant ; for as soon as its 

 hair-like branches lay hold of any living support, its 



