250 Field, Forest, and Wayside Flowers 
into the soil, and serves all the purposes of the 
first rootlet in the sprouting seed-plant. 
Meantime the larger and greener portion of the 
spore stretches out into a tube, and a little later 
partitions grow across the interior of this tube, cut- 
ting it up into a chain of cells. Later still the 
cell at the outermost end divides into two by a 
lengthwise partition. Then all the cells begin to 
divide lengthwise and crosswise by the growth of 
delicate walls within them, till there is formed a 
sheet or plate of tissue, with the general outline of 
a flattened heart. Toward the centre of this 
heart, on the side which lies undermost, rows of new 
cells are now produced by the growing and splitting 
of old ones, till a cushion of tissue is formed. 
And the under surface of the little heart also 
gives rise to a number of long, slender tubes, as 
fine as hairs, which are called ‘‘ root-hairs,” because 
their office is the same as that of the roots of 
higher plants (Fig. 68). 
They anchor the little heart to the spot where it 
grew, and they help to sustain its life by absorb- 
ing moisture from the soil. 
The mass of cellular tissue resulting from the 
development of the spore is called a prothallium, 
or prothallus. 
