CHAPTER VIII. 



OF TEMPERATURE. 



LIMITS OP TEMPEEATTJIIE ENDTJEABLE BT PLANTS. — ^EPEECTS OP A TOO 



HIGH lEMPEEAIUKE. — OP A TOO LOW TEMPEEAItntE. PEOST. — ALTEE- 



NATIONS OP lEMPEEATTJEE. — ^DAT AND NiaHT. — ^WINTEE AND SUJIMEE. 

 lEMPEEATtTEE OP EAETH AND ATMOSPHEEE. 



The extreme limits of temperature which vegetables are 

 capable of bearing, without destruction of their vitality, have 

 not been determined with precision; it is, however, known, 

 that, on the one hand, certain seeds may be boiled without 

 being killed, and that, on the other, they are capable of bearing 

 many degrees of freeziag without suffering. In Hke manner, 

 some plants are found to endure the most intense cold knowa 

 upon the globe, while others sustain, occasionally, a tempe- 

 rature as high as 140°, as was observed by Dr. Coulter on the 

 banks of the Eio Colorado.* The number of plants, however, 

 capable of sustaiuing such extremes of temperature is small, 

 and the greater part of the species known to us are proved to 

 exist within the limits of 83° and 90°. What amount of tempe- 

 rature a given species will prefer, under different circumstances, 

 seems reducible to no general rule, but has to be determiaed 

 experimentally in each case, or is judged of by the known cKmate 

 of which a plant may be a native. It is probable that every 

 species has a constitution better suited to some particular 

 amount of temperature than to any other, although it can bear 

 a greater or less degree without sustaining injury. 



Although many plants will live in a temperature much below 



* The temperature borne by OsclUatorias in thermal springs is much higher than 

 this ; but no such power is posacssed by cuUimable plants. 



