116 PLANT STRUCTURES 
such as the Ivy, this bending away from the light is 
very marked; the stem presses closely to the bark or 
stone on which it creeps, probing every cranny, and 
the numerous rootlets by which it is attached are 
developed only on the dark side. But when the plant 
is old enough to flower, then branches devoid of roots 
grow out towards the light, so that the blossoms may 
be borne in the open, where they may be seen and 
visited by the numerous insects which, in their search 
for nectar, pollinate them. 
In contrast to the extreme development in length 
found in the stems of climbing plants the extreme 
reduction of stem found in many plants of dry places 
may be referred to. The Crocus, for instance, has an 
abbreviated upright stem of which each year’s growth 
is distended for the storage of food: one year’s 
growth dies away as the next enlarges, so that the 
well-known bulb-like corm is produced. Compare the 
“roots ”—really the stem—of Montbretia, in which 
the annual growths remain, the result being a knobby 
structure like a string of onions. In bulbs reduction 
in length is carried still farther, the stem forming a 
broad cone from the surface of which spring a number 
of modified leaves, forming fleshy scales swollen with 
food material; these surround and protect the bud, 
which when it grows produces green leaves and a 
terminal flower-shoot; growth is continued by axillary 
scale-leaved shoots situated among the scale leaves, 
which in due course themselves produce green leaves 
and flowers. These compact food-charged stems take 
up their position well below the ground, out of reach 
of intense heat or drought, and during the favourable 
season send up rapidly into the air their leaves and 
