CHAPTER XXVIII 

 SPERMATOPHYTES 



THIS is the highest group of plants and is characterized by 

 the production of seeds. The plants belonging to this group 

 possess highly 1 developed organs, such as roots, stems and leaves, 

 composed of the highly differentiated tissues which we have 

 already studied (Chapter II). The Gametophyte plant body 

 is very small and the Sporophyte plant body very large. Fur- 

 thermore, the Gametophyte body is dependent on the Sporo- 

 phyte body, which is exactly the reverse of the conditions found 

 in the Bryophytes and Pteridophytes. 



The principal divisions of the Spermatophytes are shown 

 on page 304. 



The Gynwsperms are not so highly developed as the Angio- 

 sperms and possess characters showing their close relationship to 

 the Pteridophytes. They were much more important in past 

 ages than at present time and many of the ancient species are 

 now extinct. 



The Cycadales are tropical plants and are very closely re- 

 lated to the Pteridophytes. The most familiar species is Cycas 

 revoluta. (Fig. 151), which is very frequently grown in green- 

 houses. The sporophyte is a columnar stem, bearing at its apex 

 a number of large fern-like leaves. It bears a close resemblance 

 to the tree ferns. In some of the small species, the stem is small 

 and underground, while in some of the large species it may be as 

 much as fifty feet in height. The cycads bear cones (or strobili) 

 very similar to those on the pines. The staminate stro- 

 bili are composed of microsporophylls, bearing microsporan- 

 gia, which contain microspores. The pistillate strobili are 

 composed of macrosporophylls, bearing macrosporangia, con- 

 taining the macrospores. 



303 



