858 BIOLOGICAL TRAINING AND STUDIES. 



to life when the deep strata into which they are thus introduced, 

 and in which they are sealed up as the chasms close up, come in 

 any way to be laid open to the unimpeded action of the sun and 

 moisture. Squirrels, again, and some birds resembling herein the 

 rodent mammalia, bury seeds and forget to dig them up again ; 

 and it is supposed that they may bury them so deep as to be pro- 

 tected from the two physical agencies just mentioned. Now ger- 

 mination cannot take place in the absence of oxygen ; and I would 

 add that well-sinkers know to their cost how often the superficial 

 strata of the earth are surcharged with carbonic acid. The rival 

 explanation and the less popular (I do not say the less scientific) 

 looks to the agency of transportation as occurring constantly, and 

 sufficing to explain the facts. By accepting this explanation, we 

 save ourselves from running counter to certain experiments, some 

 of which were carried out, if I mistake not, under the auspices of 

 this Section (see ' Brit. Assoc. Reports '), and which appear to 

 curtail considerably the time during which seeds retain their 

 vitality, and to multiply considerably the number of conditions 

 which must be in force to allow of such retention for periods far 

 shorter than those which have to be accounted for. A better 

 instance of the expediency of checking the interpretations based 

 merely upon observations, however accurately made, by putting 

 into action experiments, cannot be furnished than by recording 

 the fact put on record by Mr. Bentham, when discussing this 

 question in his last year's Address to the Linnean Society : — 



'Hitherto direct observation has, as far as I am aware, only 

 produced negative results, of which a strong instance has been 

 communicated to me by Dr. Hooker. In deepening the lake in 

 Kew Gardens they uncovered the bed of an old piece of water, 

 upon which there came up a plentiful crop of Typha, a plant 

 not observed in the immediate vicinity ; and it was therefore con- 

 cluded that the seed must have been in the soil. To try the 

 question, Dr. Hooker had six Ward's cases filled with some of the 

 soil remaining uncovered close to that which had produced the 

 Typha, and carefully watched ; but not a single Typha came up in 

 any one of them.' (Note in President's Address, May 24, 1869, 

 p. Ixxii of ' Linnean Society's Proceedings.') 



To this I would add that experiments with a positive result, and 

 that positive result in favour of the second hypothesis, if hypothesis 



