494 General Botany 



In all three phyla the production of two kinds of spores (heter- 

 ospory) occurs either in the modern representatives or in the fossil 

 forms. 



Among the ferns the leaves are often extremely large and are 

 characterized by forked venation. During development the 

 leaves uncoil, as the growing points are in the tips of the leaves and 

 leaflets. The leaves of the lycopods are poorly developed, being 

 only scales, and those of the equisetums are scales devoid of 

 chlorophyll. 



The roots of Pteridophytes are usually small and scattered 

 along the horizontal stems. In the large, upright tree types 

 they are generally basal and sometimes of considerable size, but 

 even then they do not compare with those of the seed plants in 

 relative absorbing area. 



All of the phyla have forms in which the spores are not pro- 

 duced on foliage leaves. The special spore-bearing leaves are 

 reduced in size and in extreme forms lack chlorophyll. These 

 leaves are termed sporophylls. In the equisetums and lycopods 

 the sporophylls are arranged in cones. The extreme forms also 

 have two kinds of sporangia and spores : microsporangia and 

 microspores, and megasporangia and megaspores. 



REFERENCES 



Atkinson, G. F. Biology of Ferns. The Macmillan Company, New York. 



Campbell, D. H. Structure and Development of Mosses and Ferns. The Mac- 

 millan Company, New York; 1918. 



Clute, W. N. Our Ferns in Their Haunts. F. A. Stokes Company, New York; 

 1901. 



Waters, C. E. Ferns. Henry Holt & Co., New York ; 1903. 



