82 
TEMPERATURE. 
management must be attended with disastrous consequences, it 
may be advisable to give some attention to its mode of operating, 
and the best means of directing it to our advantage. 
The excitability of a plant or its power of growing always 
commences with a rise of temperature,' and is continued through 
the same means. The amount of heat necessary for its healthy 
progression varying according to the normal character and 
native position of each individual. The extremes of temperature 
between which cultivated plants will flourish may be stated as 
32° and 90°; below the former no vegetation that we are 
acquainted with can grow, though some from alpine regions, and 
even among our own indigenous weeds species may be found, as 
the common chickweed and groundsel, which certainly extend 
themselves when the temperature is not a whole degree above the 
freezing point. 
The recorded instances of plants living and growing under the 
opposite extreme are but few ; the highest point at which terrestrial 
plants have been found in a state of nature is 140°, as was observed 
by Dr. Coulter on the banks of the Rio Colorado, but with such 
cases we have now nothing to do, that more immediately requiring 
attention being the more limited range first mentioned. 
It is well known that plants naturally adapted to any pecu¬ 
liarity of temperature, will not bear an excessive change and 
continue to live, nor are instances rare in which comparative 
slight variations during the period of active existence have, when 
of frequent recurrence, terminated fatally. The effects of an 
excessively high temperature bear a close resemblance to the 
debilitation occasioned by intemperate living on the animal frame; 
an unsuitably high moist atmosphere causes an extension of the 
tissue, beyond the power of the vital energies of the plant to 
solidify; the ducts become gorged with crude sap, which remains 
unassimilated; its powers of action are deranged, enfeebled, 
and finally stopped ; debility, disease, and death ensue, as a finish 
and natural end to the immoderate supply of what under proper 
regulations would have been the source of life, health, and fruit¬ 
fulness. 
The consequences of excess in what may be called minor cases, 
where it is not carried to so fatal an extent, are also much to be 
feared; the natural tendency of every superfluous degree of heat 
