OTHER PLANTS THAN OURS It 
broad and beautiful panorama spread around, we must 
for a moment try to take a wider outlook than 
Him that vexed his brains, and theories built 
Of gossamer upon the brittle winds, 
Perplexed exceedingly why plants were found 
Upon the mountain-tops, but wondering not 
Why plants were found at all, more wondrous still ! 
I trust the paraphrase may be pardoned. Why, in- 
deed, should there be plants at all? This great globe, 
with its whole land surface covered, save at the Poles 
and in desert regions, with green plants in ten 
thousand forms, is indeed something to be wondered 
at. One fascinating question that arises is this: How 
far is our “lukewarm bullet” unique in its possession 
of a green plant mantle? Have we any evidence for 
the supposition that plants exist on the Moon, or on 
any planets of the solar system other than the Earth? 
Vegetation as we know it on our world requires 
certain physical and chemical conditions for its exist- 
ence. For instance, a temperature which, at least 
during the growing season, is well above the freezing- 
point of water is requisite; yet the temperature must 
remain a long way below the boiling-point of water ; 
neither could plants as we know them exist in the 
absence of an atmosphere containing oxygen, carbon 
dioxide, and water vapour, and incidentally, by its 
capacity for retaining heat, warding off violent ex- 
tremes of temperature which otherwise would be a 
daily and nightly occurrence. What evidence is there 
as to the condition in these respects of those 
heavenly bodies which are sufficiently near to allow 
us to know something of them? To take first our own 
Moon. Astronomers are agreed that on the Moon 
