56 AN INTRODUCTION TO THE STUDY OF FOSSILS 



lower groups is not, however, so great as at first appears. There 

 is the same alternation of the vegetative (asexual) and repro- 

 ductive (sexual) generations, the sporophyte and the gameto- 

 phyte, as is seen in the Pteridophyta, but the alternation is less 

 evident. Inequality between sporophyte and gametophyte is 

 still more pronounced than in the fern. 



The " seed " is the beginning of the sporophyte stage; the 

 embryo within it later unfolds into the mature plant. In 

 specialized organs within the flower or cone there are developed 

 the sporangia, either male or female. The female sporangium 

 is called the ovule, and the male the anther sac. From these 

 sporangia are discharged the spores, — the pollen from the 

 anther sacs, a specially differentiated cell from the ovule ; these 

 spores develop either into the male or the female gametophyte 

 as the case may be, and from the union of their products results 

 the fertilized ovum, — the seed. All the process of formation 

 of the gametophyte takes place within the flower. For discus- 

 sion of this process see page 77. 



Derivation of name. — Greek sprrma, seed + phyton, plant. 

 The members of this division are distinguished by the production 

 of seeds. 



The spermatophytes are divided into : Page 



A. Gymnospermae 56 



B. Angiospermae 75 



SUB-DIVISION A, GYMNOSPERiVLE 



In these plants the seeds are unprotected by any covering. 

 This character is indicated by the derivation of the name from 

 the Greek gymnos, naked + sperma, a seed. 



Trees and shrubs, mostly evergreen. They include the fol- 

 lowing orders : 



a. Cycadofilicales. 



b. Cycadales : 



1. Cycadeoideae. 



2. Cycadeae. 



