Winifred E. Brenchley 3 



oxygen supply, etc. Becquerel^ states that the resistance of seeds to low 

 temperatiue depends solely on the quantity of water and gas in their 

 tissues. If this quantity is sufficient the cold disorganises the protoplasm 

 and nucleus, so killing the seeds, but if the protoplasm has attained by 

 desiccation its maximum concentration anil consequently its minimum 

 of activity it completely escapes the action of low temperature and does 

 not freeze, so that the seed retains its power of germination. If this be 

 the case, immature seeds are likely to lose their power of germination 

 quite soon after burial from the effects of cold, whereas mature seeds of 

 the same species may be able to withstand the low temperature of winter 

 for long periods of years. Vines^ considered that long continued e.xposure 

 to a not very low temperature proves fatal, and he stated that under 

 ordinary circumstances starchy seeds retain their power of germination 

 much longer than oily seeds. This latter statement is at variance with 

 the commonly accepted idea, as it is usually considered that the oil in 

 the seeds is of special assistance in the retention of vitality. 



Under certain conditions the seeds of many species of plants are able 

 to remain dormant in the soil for long periods, and to start into growth 

 when they are brought to the surface by the processes of cultivation. 

 The popular imagination often runs riot in this connection and stories are 

 told of great crops of charlock, poppy and other weeds which appear 

 when "old pasture" or "land which has never grown charlock before" is 

 broken up. Careful enquiry usually shows that the "old pasture" was 

 under tillage at no very distant date, or that the land that was supposed 

 to be free from charlock has been ploughed rather more deeply than usual. 

 Nevertheless, some evidence cannot be explained away thus, and much 

 enquiry and experiment will be necessary before a full and satisfactory 

 explanation is forthcoming. Similar reports come from other countries 

 than England. Brulalettc d'Abbeville^ stated that alders appeared on 

 some excavated soil although none had been known in the district for two 

 centuries. According to Maquin-Tandon* soil that was thrown up in 

 digging a canal at Toulouse was covered in two years with Pohjpogon 

 monspicliensis, a plant which is lacking in Toulouse. Trochu^ cites an 

 instance in which sarrasin and millet came up when the soil was disturbed 

 in an orchard which had been established for 10 or 12 years, the species 

 having been originally sown as crops. In the same orchard, when 

 trenches were dug to root prune the trees, heath and furze came up from 



1 Tmc. cii. 



^ Vines, Physioloipj oj PUmts, 



' Quoted by Becquerel, loc. cit. 



