LIFE HISTORY OF A FERN. 233 



lands connecting rather than separating these clases, in whicli it is 

 exceedingly difficult even for the scientist to say with certainty to 

 which class the object under examination may belong. 



Confining ourselves now, however, to the great division of 

 Vegetables — to which Ferns undoubtedly belong — we may fairly 

 ask what position in that class they occupy, for its range is so 

 extensive that it embraces every form of vegetable life from the 

 simple unicellular alga, which appears as a green slime upon the 

 surface of a stagnant pool, or the powdery mould on some damp 

 substance, to the most perfect flower which finds a home on the 

 table of royalty, or the gigantic monarch of the forest which for 

 centuries has upreared its leafy head and outstretched its mighty 

 arms, a monument of strength and beauty. We may, therefore, 

 look for a moment at the classification now generally adopted, as 

 it may assist us in comprehending the several successive steps by 

 which we rise from the most simple to the most complex forms of 

 vegetable life. 



Outlines of Classification. 



I. — Thallophytes. — Algae, Fungi, Lichens. — The vegetative 

 body, usually a thallus — i.e., it exhibits no differentiation 

 into stem, leaf, and root. 



II. — MusciN^. — Liverworts, Mosses. — Sharply defined alterna- 

 tion of generation. 



III. — Vascular Cryptogams. — Ferns: EquisetacecB^ OphioglossecB^ 

 Rhizocarpece, LycopodiacecB, Selaginellece, Iso'etece. Life-his- 

 tory divided into two generations, extremely different, both 

 morphologically and physiologically. From the spore pro- 

 ceeds a sexual generation — i.e., a prothallium bearing 

 anteridia and archegonia. From the fertilised archegonia 

 proceeds a plant without sexual organs, but in their place a 

 number of spores. 



IV. — Phanerogams. — Gymnosperms (naked seeds), Coniferae, etc. 

 Angiosperrns (seeds in an ovary). Monocotyledons, Dico- 

 tyledons. 



It will now be seen that Ferns occupy an almost central posi- 

 tion in the scale, midway between the elementary unicellular 

 algce, which ^re scarcely more than a simple mass of protoplasm, 



