(45) 



that has recently been burnt over, as species of Funaria 

 and Leptobryum, while others grow only on the bones of 

 dead animals or in places where animal refuse has accumu- 

 lated. 



Next higher in the plant kingdom is the subkingdom 

 Pteridophyta, or ferns and fern-allies, the seedless plants 

 with roots, stems, leaves, and woody tissue (cases 49 to 

 55). The ferns as a group perhaps attract the attention 

 of a greater number of people than any other series of 

 plants. Associated with what are usually known as ferns 

 are the fern-allies, for example the "horse-tails" {Equi- 

 setum), "lycopods" (Lycopodium), and "quillworts" 

 (Isoetes), but these are usually less conspicuous than the 

 "ferns." Fern-plants differ from all the plants of simpler 

 organization in having vascular (woody) tissue, that is, 

 a system of vessels for conducting sap through the different 

 parts of the plant-body. They exhibit an almost infinite 

 variety of form; their stems may be underground, hori- 

 zontal on the ground, or erect; the leaves are either simple 

 or compound, and sometimes perform both the work of 

 foliage leaves and that of bearing the spore-cases (ferns), 

 while in other cases some of the leaves have become changed 

 into mere spore-bearing organs (cinnamon-fern). 



The "flowering" plants (cases 56 to 128) comprise a 

 single subkingdom, the Spermatophyta, or seed-bearing 

 plants. This extensive group seems to have followed two 

 independent lines of development and consequently the 

 plants fall into two well marked groups, the first being 

 the gymnosperms, cone-bearing plants, or plants in which 

 the seeds are borne exposed in variously shaped cones 

 (cases 56 to 58). This is a comparatively small group, 

 but exhibits great diversity, including plants ranging from 

 straggling shrubs or vines to the largest trees. The leaves, 

 too, vary from structures resembling needles or scales to 

 expanded fern-like structures of considerable variety. 

 In a former geological age these plants were the dominant 

 seed-bearing plants, but now the second group of the sper- 



