•78 • PROCEEDINGS OF THE ACADEMY OF [1884. 



have appeared since the recession of the ice, or whether they 

 managed to retain their hold during the whole continuance of 

 the ice-sheet. 



At our landing place a small stream entered the ocean, and 

 this stream came through a swampy vallej^ a few hundred feet 

 wide, extending into the land for an unknown distance. The 

 hills of drift were on each side of this valley. All the planfcs were 

 collected within a quarter of a mile of the mouth of this stream, 

 and there is every reason to believe that a larger number of 

 species might have been collected had there been time or oppor- 

 tunity for more inland research along its line. By the margin of 

 the swamp were rocks from five to ten or twenty feet above its 

 ground level, and not covered by drift ; but on the more level 

 rocks often with a few feet of sand, which had evidently blown 

 in during the course of years. Yet with every opportunity to 

 do so had there been time for the work, very few of the plants 

 along the line of the stream had extended to the drift deposits 

 close by. These plants were not brought there by the drift. We 

 may say almost with certainty that they were there during the 

 period when the land was covered by ice. How did they manage 

 to maintain themselves under these circumstances ? Were they 

 wholly covered by ice ? or were there rifts and clefts in the ice- 

 sheet deep enough to allow plants a summer of recuperation? 



I think we need not regard the last consideration as one of 

 necessity. There is reason to believe that under a low tempera- 

 ture plants will retain vital power for an indefinite period. Mr. 

 Douglas, of Waukegan, Illinois, once sent to me young trees of 

 Gatalpa speciosa, that had been placed in sand in a cool cellar and 

 forgotten a year, and that remained the whole twelve months 

 dormant, and grew the next year when planted out. Dr. Max- 

 well T. Masters, of London, has called attention to the case of 

 aii orchid which, as I remember, remained under ground a whole 

 season without growing, and this has been adduced as a probable 

 explanation of the non-appearance in some seasons of plants 

 which are plentiful in others. If a plant will remain dormant 

 one, two or three years under unfavorable conditions for growth, 

 who shall say how much longer a period the}' ma}' not live, 

 under conditions favorable to dormancy onl}' ? I have a strong 

 suspicion that just at or below the freezing-point roots may live 

 for an unlimited number of years ; and that a district might be 



