ca he » Life - the Plant. ; 200° 
the winter, as the Christmas rose Sad hepatica, frets when the tempera- 
ture falls below zero at any stage of their growth, which begins again 
as soon as they thaw. ‘The extraordinarily rapid growth of Alpine 
and Arctic plants in spring depends on a long anterior development of 
their floral organs in the preceding autumn. ‘The green sods and the 
great number of leafy plants which appear as soon as snow melts, only 
show that the number of evergreen plants is larger than is generally 
supposed. Growth is entirely dependent on the atmosphere ; hence 
the blooming of willows and rhododendrons whose roots and stems are 
still frozen, as well as the development of the so-called ‘ red snow,’ the 
Alga Protococcus (Palmela) nivalis, on the surface of the snow. Neither 
the lowest nor the highest temperature at which plants can exist has yet 
been determined. It would appear, however, that water must not be 
above 40° C. for plants to be able to live in it. Plants living in the 
air, on the other hand, will endure for some time a temperature of from 
48° to 49° C. ; at 51° they.are killed in from 10 to 30 minutes. ! 
The growth of the embryo at the expense of the reserve-materials 
stored up init, begins, with wheat and barley, at about 5° C.; with 
the scarlet-runner and maize at 9°°4; with the pumpkin, Cucurbita Pepo, 
not below 13°°7 C. But when the reserve-materials have been. con- 
sumed, a higher temperature is apparently always necessary to enable 
srowth to proceed by means of freshly assimilated material. The 
highest temperature at which germination can take place is about 
42° C, for the scarlet-runner, maize, and pumpkin ; 37° to 38°C. for 
wheat, barley, and peas. 
The lowest temperature at which the chlorophyll-bodies turn green 
is above 6° C. in the scarlet-runner and maize; between 7° and 11° 
C. for Pinus pinea ; and the highest at which leaves already formed. 
and still yellow turn green is above 33° C. The cold of winter often 
occasions a winter-colouring in evergreen plants. This is caused: (1) 
by a brown colouring, in consequence of a peculiar transformation of the 
blue-green constituent of chlorophyll, as in Conifers: and the box ; 
(2) by a red colouring, in consequence of the formation of a red pig- 
ment soluble in water and imbedded in balls of tannin, as in A/Zahonia; 
(3) by a change in colour of the chlorophyll itself by the shifting and 
collecting into masses of the grains of chlorophyll; this occurs in all 
plants. A higher temperature restores the normal condition. _ 
The exhalation of oxygen and consequent assimilation begin, in 
1 [A few Algze of low organisation appear to be able to withstand a 
temperature of nearly or quite boiling water ; as do also some F ungi, 
as Bacteria, and fungus-spores.—ED. ] 
BP 
