340 
FERNS AND THEIR ALLIES 
changed into coal. At the same time natural gas and 
petroleum, or rock oil, were formed. No coal is being formed 
at the present time, and when our supply is exhausted 
we shall have to find other 
sources of heat and power. 
Peat, found in old bogs, 
consists largely of vegetable 
matter. When dried it can 
be used as fuel. 
SUMMARY 
Ferns and their allies are 
less dependent on water than 
are the algae, fungi, and 
mosses. They are more 
highly organized, as they 
have epidermis, stomata, me¬ 
chanical tissue, conductive 
tissue, stem, roots, and leaves. Their life history shows the 
alternation of generations, consisting of spore, protonema, 
pro thallium, and sporophyte. Club mosses, horsetail, and 
selaginella are closely related forms. Coal was formed from 
ferns which grew to the size of trees in regions which were 
then hot and moist. 
QUESTIONS 
What parts of the flowering plant are found in the fern? In an 
animal what corresponds to epidermal tissue? to conductive tissue? 
to fundamental tissue ? to mechanical tissue ? Compare the life history 
of a moss and a fern. Why can ferns do with less water than mosses? 
Illustrate by diagrams or sketches the life history of a fern. What 
plants are related to ferns? Tell how coal beds were formed. 
REFERENCES 
Bergen, Foundations of Botany, pages 277 and 286. 
Campbell, A University Textbook of Botany, pages 200 and 241. 
Curtis, A Textbook of General Botany, Chapters VII and VIII. 
Leavitt, Outlines of Botany, pages 198 and 204. 
Figure 315.— Cross Section of 
Stem of Equisetum. 
A , air passage; B, furrow; C, ridge; 
D, central air passage : E, vascular 
bundles. 
