1905-1906.] The Great Gulf. 261 



sort of Jekyll-and-Hyde existence. From the spore grows 

 what is called a prothallus — a flat, heart-shaped, green object, 

 not unlike a piece of the frond of Pellia epiphylla. 

 The under side is attached to the ground by rhizoids, and 

 on this side also are found sexual organs termed antheridia and 

 archegonia. The antheridia, or male organs, consist of minute 

 rounded protuberances, composed of a number of cells, each 

 containing a spermatozoid. These latter are excessively 

 minute spirally- coiled bodies like corkscrews, but thicker at 

 one end than the other. Near the thin end a number of 

 exceedingly fine cilia are attached. When the anthei'idia are 

 ripe they burst on contact with water, the spermatozoids are 

 set free, and at once begin swimming about in the water with 

 the aid of their cilia. 



The archegonia are minute sacs buried in the prothallus, 

 with an opening to the exterior by means of a hollow neck 

 projecting slightly beyond the surface. At the bottom of the 

 sac is found a cell containing an ovum. When the ovum is 

 ripe the spermatozoids are attracted to the opening at the end 

 of the neck, down which they make their way until they reach 

 the ovum, which is thus fertilised. The ovum immediately 

 begins to develop and grow, eventually becoming a male fern, 

 with fronds and spores ready to repeat the life- cycle once 

 more. 



Here, then, is a deeply interesting and strange life-history. 

 First we have the spore-bearing plant, or sporophyte, being 

 the ordinary male fern, which has no sexual organs and does 

 not reproduce itself, but from a spore of which grows the 

 prothallus, being the oophyte or ovum-bearing plant. The 

 prothallus in turn does not reproduce itself, but by means of 

 sexual organs produces the fern or sporophyte. 



Stepping now across the gap between the vascular and 

 cellular cryptogams, let us take an example from the family 

 in the latter group, nearest allied to the ferns, namely, the 

 mosses. A good one is found in a very common moss, 

 Funaria hygrometrica, an acrocarpous moss growing gregari- 

 ously in large patches, especially where wood has been burned 

 on the ground. Another example, and a very handsome moss, 

 is Hylocomium splendens, one of the hypnoid group of pleuro- 

 carpous mosses. From these specimens it will be observed 

 that mosses roughly consist of two main types — first, one 



