26o The Great Gulf. [Sess. 



the latter being lower in the scale of life than the former. 

 These groups are again divided — the Cryptogams into two, 

 namely, (1) the Vascular Cryptogams, or those partly composed 

 of vascular tissue ; and (2) the Cellular Cryptogams, or those 

 composed of cellular tissue entirely. The Vascular Cryptogams 

 divide into several well-marked Natural Orders, the most dis- 

 tinctive of which are (1) the Lycopodiums, or club-mosses ; 

 (2) the Eqiiisetums, or horsetails ; and (3) the Filices, or ferns. 

 The Cellular Cryptogams break up into a large number of 

 Natural Orders, at the head of which we find the Bryacese, or 

 mosses, followed by a long list of other Orders. Here, then, 

 between the Vascular and Cellular Cryptogams we find the 

 great gulf, — an arch, or several arches, being required to bridge 

 the chasm that lies between them. Let us see exactly how 

 wide this chasm is. 



For our present purpose we cannot do better than take the 

 ferns as a type of the Vascular Cryptogams. Here is Nephrod- 

 ium Filix-mas, the common male fern, which is familiar to 

 everybody who takes an interest in our native flora. This 

 fern consists of a short brown stem surmounted by a cup- 

 shaped crown of beautiful green fronds, much divided. It 

 derives its nourishment, like most other plants, partly from 

 the soil by means of its roots, and partly from the air by its 

 fronds. With the question of nourishment we have nothing 

 to do. What concerns us is the reproduction or life-history 

 of the plant. On the back of the fronds you will see a number 

 of small brown heaps named sori, each with a covering called 

 an indusium. This is shaped like a kidney, and hence the 

 generic name of the plant, derived from the Greek nephros, 

 a kidney. Under the indusium the heaps are composed of a 

 number of small brown cases, termed sporangia or thecae, and 

 these again are filled by a vast number of minute round bodies 

 called spores. How minute they are may be judged from the 

 fact that it would take at least 250,000 of them to cover a 

 square inch of surface ! 



When they arrive at maturity, the sporangia, or spore-cases, 

 burst, and the spores are set free. If they fall on, or are 

 carried to, a suitable place, these spores germinate and 

 begin to grow. Now, one would naturally suppose that 

 from the spore grown upon a fern would grow another fern, 

 but this is not so. Our friend the fern leads a double life, a 



