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. 



