THE FERN'S PLACE IN NATURE. 49 



recognized, we find two types of plants of lower grade which 

 stand out prominently to even the unpracticed eye. Of these 

 the first are mostly green,* and though variously known and 

 named may be called collectively alga. Like the higher plants, 

 these low forms maintain an independent existence, drawing 

 their nourishment directly from the air and water. Of the 

 second group we may find examples in the mildew that spreads 

 its white cobwebby film over the leaves of the lilac, the willow 

 and other plants ; or in the rust, red or black, that injures our 

 fields of standing grain ; or in the black smut that often re- 

 places the ears of corn and greatly disfigures the plant. Other 

 examples may be seen in the shelving masses that protrude 

 from old stumps or logs, or in the bright scarlet cups that ap- 

 pear on the ground in rich woods in earliest spring. Whatever 

 the color of these forms of plant growth, they may be charac- 

 terized as not green. They represent a group of plants that 

 require nourishment from some source besides air and water; 

 some are parasitic drawing nourishment from living plants or 

 animals, while others are saprophytic living on decaying or- 

 ganic matter. Though widely differing in character, we may 

 call them all fungi. In addition to these forms are the lichens 

 which are intimately related to some of the groups of fungi 

 and cannot be considered as forming a definite group by them- 

 selves. 



1 25. Looking over this array of forms we find that with all 

 their diversity they may be arranged somewhat naturally in 

 four groups as follows, commencing with the highest : 

 I. SPERMAPHYTES. (Seed-bearing plants.) 

 II. PTERIDOPHYTES. (Ferns and their allies.) 



III. BRYOPHYTES. (Mosses and Liverworts.) 



IV. THALLOPHYTES. (Algae, Lichens and Fungi.) 



It will be observed that the last three are all spore producers 

 instead of seed producers like the flowering plants of the first 



* Observant visitors at the seaside are familiar with the brown, purple and 

 bright red "sea-weeds" that belong here but have their fundamental green 

 color masked by other coloring matters. These are sometimes called "sea 

 mosses," which is another unfortunate and confusing use of a term which 

 ought to be confined to its particular group. 



