GERMINATION — EEQUISITES FOE IT. 345 



place in the seed. Dry seeds -will not germinate. Until water be 

 absorbed no circulation of fluids in the seed can take place. The 

 quantity of water absorbed by seeds is often very large. Decandolle 

 found that a French bean, weighing 544 mUlegrammes, absorbed 756 

 of water. The swelling of Peas by absorption of water is familiar to 

 all. The- kernels or seeds of stone-fruits by this means are enabled to 

 burst their hard coverings. 



The temperature required for germination varies in different seeds. 

 Some demand a tropical heat, others are satisfied with the warmth 

 of our spring. In general, the requisite temperature may be said to 

 vary from 60° to 80° F. Some seeds can bear a temperature which 

 would kill others. Some have been known to germinate after ex- 

 posure for a short time to the heat of boiling syrup ; others after 

 exposure to a cold of -39° F. Cereals and beans can only bear 

 immersion in water at 110° F. for a few minutes. In steam they 

 will bear 140° F. ; and in dry air 170° F. Many plants grow in the 

 immediate vicinity of very hot springs, others in cold regions. 

 Edwards and Colin, from their experiments, were led to fix 95° F. 

 as the highest limit of prolonged temperature which cereal grains can 

 bear in water; and 113° P. as the highest they can bear in sand or 

 earth. Vegetable life has been observed progressing under much 

 higher temperatures. In the Manilla Islands, a hot spring, which 

 raised the thermometer to 187°, had plants flourishing in it and on 

 its borders. A species of Chara grows in the hot springs of Iceland, 

 and various Confervas in the boiling springs of Arabia and of the 

 Cape of Good Hope. Dr. Hooker states that on the edge of hot 

 springs in the valley of the Soane in India, the temperature of which 

 was sufficient to boil eggs, there occurred sixteen species of flower- 

 ing plants, — Desmodium, Oldenlandia, Boerhaavia, some Compositse, 

 Grasses, and Cyperacese. Moseley noticed specimens of Botryococcus, 

 Braunia, Diatoms, and other Algse, in the hot springs of Furnas in 

 the Azores. Hooker found Confervas in the hot springs of Bel- 

 cuppee on the Behar Hills, at 168° F. Cyperacese grew in water of 

 100° P. Dr. Wood of California found Nostoc calidarium and Chry- 

 sococcus ,thermophilus in the hot springs of Benton, at 160° P. Abel 

 mentions an Arenaria growing in soil at a temperature of 110° P. 

 Cyperus polystachius and Pteris longifolia were found by Schouw 

 in very hot soil which burnt the hand. Wheat, Oats, and Barley, are 

 said to thrive in any country where the mean temperature exceeds 

 65° P. The spores of certain cryptogamic plants are especially fitted 

 for cold countries. Edwards and Colin found that seeds in a dry air 

 bore a higher temperature than in water or steam. , 



Air, or rather oaoygen, was shown by Scheele to be necessary for 

 germination. Seeds deeply buried in the soil, and excluded from 

 air, do not spring. The depth at which seeds should be sown varies 



