De HETEROMORPHY. 
trophy, Atrophy, &c., for malformations capable of 
more rigid classification than those here alluded to. 
Formation of tubes—T'he production of ascidia or 
pitchers from the cohesion of the margms of one or 
more leaves has been already alluded to (see pp. 21,30), 
but there is another class of cases in which the tubular 
formation is due, not so much to the union of the 
margins of a leaf as to the disproportionate growth of 












! Fic. 166.—Portion of the under surface of a cabbage-leaf, with horn- 
like excrescences projecting from it. 
some portions as contrasted with others, whence arises 
either a depressed cavity, as in the case of a leaf, or 
