244 Retrograde Varieties 



brambles and some garden-varieties of the tur- 

 nip (Brassica). 



In such cases of parallel variations the single 

 instances obviously follow the same rules and 

 are therefore to be designated as analogous. 

 Pitchers or ascidia, formed by the union of the 

 margins of a leaf, are perhaps the best proof. 

 They were classified by Morren under two heads, 

 according to their formation from one or more 

 leaves. Monophyllous pitchers obey the same 

 law, viz. : that the upper side of the leaf has be- 

 come the inner side of the pitcher. Only one 

 exception to this rule is known to me. It is af- 

 forded by the pitchers of the banyan or holy 

 fig-tree, Ficus religiosus, but it does not seem to 

 belong to the same class as other pitchers, 

 since as far as it has been possible to ascertain 

 the facts, these pitchers are not formed by a 

 few leaves as in all other cases, but by all the 

 leaves of the tree. 



In some cases pitchers are only built up of 

 part of the leaf-blade. Such partial malforma- 

 tions obey a rule, that is common to them and to 

 other foliar enations, viz. : that the side of the 

 leaf from which they emerge, is always their 

 outer side. The inner surface of these ena- 

 tions corresponds to the opposite side of the 

 leaf, both in color and in anatomical structure. 



The last of the four rules above mentioned is 



