Taxonomic Anomalies 671 



lobes, the deeper the ascidium will become. It 

 should be added that this explanation of the dif- 

 ferent shapes of ascidia is of general validity. 



Ascidia of the snake-plantain or Plantago 

 lanceolata are narrow tubes, because the leaves 

 are oblong or lanceolate, while those of the 

 broad leaved species of arrowhead, as for in- 

 stance, the Sagittaria japonica, are of a conical 

 shape. 



From the evidence of the lime-tree we may 

 conclude that normal peltate leaves may have 

 originated in the same way. And from the fact 

 that pitchers are one of the most frequent 

 anomalies, we may conclude that the chance of 

 producing peltate leaves must have been a very 

 great one, and wholly sufficient to account for 

 all observed cases. In every instance the pre- 

 viously existing shape of the leaf must have de- 

 cided whether peltate or pitcher-like leaves 

 would be formed. As far as we can judge pel- 

 tate anomalies are quite injurious, while ascidia 

 are forms which must impede the effect of the 

 light on the leaf, as they conceal quite an impor- 

 tant part of its upper surface. In this way it is 

 easily conceivable that peltate leaves are a fre- 

 quent specific character, while ascidia are not, 

 as they only appear in the special cases of 

 limited adaptation, as in the instances of the 

 so called pitcher-plants. The genera Nepenthes, 



