LIFE HISTORIES 17 



known as the prothallus, which is responsible 

 for the sex organs. The process of cell-division 

 goes forward and ultimately results in the 

 development of a green scale measuring, 

 perhaps, an eighth of an inch across at its 

 broadest part. This is the fully-grown pro- 

 thallus. From the underside arise more root 

 hairs, and it is here also that the antheridia 

 (male organs) and the archegonia (female 

 organs) are produced. As a rule, both kinds 

 of organs occur on the same prothallus, 

 although now and again prothalli have been 

 discovered which are exclusively male or 

 female. The matter is of interest, because it 

 evidences an occasional distinction of sex 

 which has become habitual in some of the 

 Club Mosses. In the case of a perfectly normal 

 prothallus the male organs or antheridia are 

 to be found amongst the root hairs, whilst 

 the female organs or archegonia arise from a 

 cushion, several cells deep, more towards the 

 centre of the process. 



The manner of fertilization may be briefly 

 outlined, although the observation of this is 

 beyond the ordinary student. With Ferns, as 

 is the case with nearly all the Cryptogams, 

 the fertilization takes place under water ; the 

 moisture may be the outcome of heavy rain 

 or even dew. However that may be, as soon 

 as the underside of the prothallus has become 

 thoroughly wetted the antheridia open, and 

 certain little bodies called spermatozoids are 

 allowed to escape. These are exceedingly 

 active, and are in the form of spirally coiled 

 bodies with a number of fine threads (cilia) 

 at one end. The same moisture which caused 

 the antheridia -to open also brings about the 

 opening of the archegonia. Some time ago it 



