668 Mutations 



must obviously be due to this most universal 

 agency. Indirect vicinism also plays some part, 

 and probably affords the explanation of some 

 reputed mutative productions of the variety. 

 So, for instance, in the case of Sinning, who aft- 

 er sowing the seeds of the common ash, got as 

 large a proportion as 2$ of monophyllous trees 

 in a culture of some thousand plants. It is 

 probable that his seeds were taken partly from 

 normal plants, and partly from hybrids between 

 the normal and the " one-bladed " type, assum- 

 ing that these hybrids have pinnate leaves like 

 their specific parent, and bear the characters of 

 the other parent only in a latent condition. 



Our third example relates to peltate leaves. 

 They have the stalk inserted in the middle of 

 the blade, a contrivance produced by the conna- 

 tion of the two basal lobes. The water-lilies 

 are a well known instance, exhibiting sagit- 

 tate leaves in the juvenile stage and changing 

 in many species, into nearly circular pel- 

 tate forms, of which Victoria regia is a very 

 good example, although its younger stages do 

 not always excite all the interest they deserve. 

 The Indian cress (Tropaeolum), the marsh- 

 pennywort or Hydrocotyle, and many other in- 

 stances could be quoted. Sometimes the peltate 

 leaves are not at all orbicular, but are elon- 

 gated, oblong or elliptic, and with only the lobes 



