126 DB. DICKIE OK GERMINATION. 





K'ote of Observations and Experiments on Germination. 



Bj a. DicEi?^' M.D., r.L.s. i2 



[Eead February 16, 1865.] 



The supposed persistence of cotyledons in Welicitscliia^ and the 

 establisbed foct tbat rn. Streptocarpiis one of tbem remains during 

 the Avliole lifetime of tlie plant, assuming the appearance of a leaf, 

 are points in vegetable physiology "which need not be enlarged 



upon here. 



Having carefully traced the gci^mination oi Strep tocarpus Bexii 

 and S. primuloides^ I observed a peculiarity which seems to have 

 been overlooked in the only paper on this subject which I have 

 seen, viz. the interesting communication of Mr, Crocker in the 

 5th volume of the Linnean Society's Journal. 



The two cotyledons are at first opposite and equal in size ; in 

 One instance I have seen three ; after some time, however, they 

 become alternate, the space between the two varying somewhat 

 in different seedlings. At a more adAunced stage, the upper 

 cotyledon thus separated from its fellows begins to enlarge, the 

 other retaining its original size, and afterwards decaying. 



On first observing this separation of the cotyledons, I was of 

 opinion that it was owing to the development of an internode. 

 Tliere might be another explanation, namely this, that the one 

 cotyledon remaining sessile, the development of a petiole at the 

 base of the other would give rise to this alternation, which accord- 

 ing to one view would be real, and to the other only apparent. 

 I am inclined, however, to believe that there is true alternation 

 consequent on the development of an internode. This has rela- 

 tion to a point respecting which there has been of late some dis- 

 cussion*, viz. the nature of the descending axis, and which inter- 

 node is to be counted as the first. 



In connexion with this, it occurred to me that it might be 

 possible, by a certain kind of treatment, to lengthen the existence 

 of cotyledons in plants in which they are usually of compara- 

 tively sliort duration. Tor this purpose it ?ecmed advisable to 

 experiment on plants having large cotyledons which rise above 

 ground, become green like leaves, and for some time perform 

 similar function : I proceeded to put this to the test. 



* See a recent Number of Nat. Hist. Keview and of SiUiman's Journal. 



a 



