cinnamo7nea in any way. Sometimes they are fertile at the top 

 only, and sometimes below, while all the rest of the frond will be 

 sterile. 



Now it so happens that such fronds apparently occur most 

 frequently on plants growing where some change in the condi- 

 tions of their environments has brought about through various 

 causes an apparent loss of vitality, and the somewhat hasty con- 

 clusion has been formulated that the frondosa forms are due to 

 this and similar causes. That this is, however, a somewhat sup- 

 erficial explanation is evident from the fact that frondosa forms 

 have also occurred in situations where there had not been any 

 change in the environments, and on plants that were normally 

 healthy in every way with the usual proportion of both sterile and 

 fertile fronds beside the abnormal frondosa form. It has been 

 sometimes stated that the frondosa fronds are a later growth, but 

 that has not been my own experience. I have generally found 

 them growing with, and maturing at the same time as the nor- 

 mally fertile fronds, and last year two frondosa fronds that I was 

 watching the development of, matured in advance of the normal 

 fertile fronds on the same plant, as when I went expecting to 

 gather them, they had drooped and withered, although the other 

 fertile fronds were still erect and fresh. 



Dr. Robert T. Jackson has told me of an experience which 

 he has had with a plant that has been growing in his garden for 

 a number of years and which this year for the first time produced 

 a frond of the frondosa form. The plant is still growing under 

 precisely the same conditions it always has been, and he could 

 not discover any cause and knew of no good reason why it should 

 have developed the form this year any more than in previous 

 years. All of which goes to show that while a change of condi- 

 tions may help to bring out some latent disposition on the part of 

 the plant to vary, the real cause lies deeper, and I trust that some 

 of you will seek for and find it out. In the case of the obtusilo- 

 bata form of Onoclea, it is not so easy, notwithstanding the as- 

 surances we have received that it is the result of injury to the 

 plant. I at one time held this view myself, but have since modi- 

 fied it. It is certainly supported by what appears to be conclu- 

 sive evidence, and the evidence is conclusive so far as it goes, but 

 it does not go far enough. For while it is true that the form is 

 found most frequently under conditions where the sterile fronds 

 have been cut away, and otherwise injured, it is also true that the 



