270 



BIOLOGY 



they are thus capable of growing immediately into new plant! 

 without being united with sperms, we know that they must 

 be spores and not eggs, since eggs require fertilization before 

 they will develop. The sacs that contain them are sporangia, 

 spg. This method of reproduction is therefore evidently an 

 asexual method. 



When these spores develop they do not, however, grow 

 into a plant like the original fern, but each grows into a very 



ar 



FIG. 125 THE LIFE HISTORY OP THE FERN 



A and B, sprouting spore; C, prothallium full grown; D, section of an archegonium; E, 

 archegonium at a later stage, showing the ovum, o, and the sperm, spm, entering to fertilize 

 the ovum; F, section of an antheridium at an early stage; G, an antheridium at a later stage, 

 discharging sperms; H, the young fern, /, growing from its prothallium. 



small, flat, green leaf (Fig. 125 A to C), which clings closely 

 to the ground, as shown at H, usually not growing to more 

 than one-quarter inch in diameter, and frequently even less. 

 It has no stem, but on the under surface are a few delicate 

 hairs called rhizoids, which grow downward, fastening the 



