40 PLANT-LIFE ON LAND [CH. 



stances favour their shedding. Moreover the Bracken 

 plant itself is well able to stand even considerable 

 drought. Thus not only is it an effective and success- 

 ful plant of the land, but dry conditions favour the 

 dissemination of the spores, the production of which 

 is the final office of the plant. 



But such dry conditions do not suffice for the 

 further development of the spores. Nor do they 

 germinate directly into new Fern-plants, but into a 

 body called the prothallus, differing in texture and 

 in other qualities from the parent. Moisture and a 

 suitable temperature are necessary for its growth, 

 and it finally forms a flat green scale-like body, about 

 half an inch or less in diameter, and attached by 

 delicate root-hairs to the damp soil on which it grows 

 (Fig. 7, A). It is a physiologically independent body 

 capable of self-nourishment, but usually of limited 

 growth and duration. Its delicate texture makes 

 continued moisture a necessity for its growth, and 

 consequently it is found only in damp and shady 

 spots, where spores happen to have been carried as 

 loose dust by the breeze. This circumstance goes 

 far to determine the positions which Ferns habitually 

 hold in Nature, for as we shall see the Fern-plant 

 springs eventually from the minute green scale-like 

 prothallus. Sooner or later it bears the sexual organs 

 upon its downward surface, the male or antheridia 

 nearer the base, the female or archegonia nearer the 



