122 Bulletin 79 



in these plants only so far as the first severe cold spell is concerned. 

 The immature joints of these species which continue growth until 

 a severe freeze, are naturally killed with the first heavy frost. How- 

 ever, the matured growth of Opuntia ficus indica and Opuntia sp. 

 Burbank Special, which ceased their growth before freezing weather, 

 showed no greater resistance to cold than the matured growth of 

 plants that had made active growth until frost. 



In concluding this statement it should be said that the laboratory 

 work has been done entirely by Mr. Uphof, who is a Hollander 

 by birth and training, and has resided in this country for but a 

 few years. While he took very careful notes on his experiments, 

 it was not possible for him, without help, to write up his results 

 for publication. This fell to the lot of the undersigned, who has en- 

 deavored to state the results as Mr. Uphof understands them. Mr. 

 Uphof has gone over this paper several times with the writer's 

 help, and has made numerous suggestions to state more fully his 

 ideas. With this brief statement, the writer asks that this work be 

 regarded as Mr. Uphof's. 



J J Thornber. 



