670 Mutations 



distinct indications of complying with the gen- 

 eral law of periodicity. The first leaves are 

 smaller, with more rounded lobes, the subse- 

 quent leaves attain a larger size, and their lobes 

 slightly change their forms. In the first leaves 

 the lobes are so broad as to touch one another 

 along a large part of their margins, but in or- 

 gans formed later this contact gradually dimin- 

 ishes and the typical leaves have the lobes wide- 

 ly separated. Now it is easily understood tliat 

 the contact or the separation of the lobes umst 

 play a part in the construction of the ascidia, 

 as soon as the margins grow together. Leaves 

 which touch one another, may be affected by 

 the connation without any further malforma- 

 tion. They remain flat, become peltate and ex- 

 hibit a shape which in some way holds a mid- 

 dle position between the pennyworts and the 

 lemon-scented eucalyptus. Here we have 

 the repetition of the specific characters of these 

 plants by the anomaly of another. Whenever 

 the margins are not in contact, and become con- 

 nate, notwithstanding their separation, the blade 

 must be folded together in some slight degree, 

 in order to produce the required contact. This 

 is the origin of the ascidium. It is quite super- 

 fluous to insist upon the fact that their width 

 or narrowness must depend upon the corre- 

 sponding normal form. The more distant the 



