I2 THE STORY OF PLANT LIFE 
And amongst some plants one species is trailing 
or climbing, another erect, as in the Loosestrife 
group. 
Amongst water plants, again, some are submerged 
below and erect above the surface, showing that the 
trailing or submerged habit is original, e.g. Water 
Violet. 
Apart from the division of plants into land and 
water plants, there are groups that cannot live apart 
from others. Some of these are parasites upon the 
roots of other plants, e.g. Yellow Rattle, Eyebright, 
Bartsia on roots of grass, Dodder on the stems of 
Furze. Others live upon the nourishment of other 
plants, such as the Bird’s Nest Orchis and the Coral- 
root. 
In the struggle for existence the plant types that 
have been most successful have been the trees. 
In former geological epochs they played a great 
part, so early that it is not possible to say whether 
the tree type was evolved gradually from other types 
or not. There are traces of lowlier types and 
aquatic plants as far back, so that their derivation is 
doubtless from earlier types of plants without the 
arborescent habit. 
In the vegetation of the land, however, trees play 
a great part, and in the history of our own country it 
may be shown that England was once practically all 
forest. Hence we must consider that the other now 
widely distributed types of plants have become 
adapted to their conditions subsequently, whether 
