PAST HISTORIES OF PLANT FAMILIES 109 



plants, we can see in the Bennettitales points which 

 throw much light on the potentialities of the Cycadean 

 stock, and structures which have given rise to some most 

 interesting speculations on the subject of the Angiosperms. 

 This group is another of the jewels in the crown of 

 fossil botany, for the whole of its structures have been 

 reconstructed from the stones that hold all that remains 

 of this once extensive and now extinct family of plants. 



CHAPTER XI 



PAST HISTORIES OF PLANT FAMILIES 



IV. The Cycads 



The group of the Cycadales, which has a systematic 

 value equivalent to the Ginkgoales, contains a much 

 larger variety of genera and species than does the latter. 

 There are still living nine genera, with more than a 

 hundred and fifty species, which form (though a small 

 one compared with most of the prime groups) a well- 

 defined family. They are the most primitive Gymno- 

 sperms, the most primitive seed -bearing plants now 

 living, and in their appearance and characters are very 

 different from any other modern type. Their external 

 resemblance to the group of the Bennettitales, however, 

 is very striking, and indeed, without the fructifications 

 it would be impossible to distinguish them. 



The best known of the genera is that of Cycas, of 

 which an illustration is given in fig. 74. The thick, 

 stumpy stem and crown of "palm "-like leaves give it 

 a very different appearance from any other Gymnosperm. 

 Commonly the plants reach only a few feet in height, 

 but very old specimens may grow to the height of 30 ft. 

 or more. The other genera are smaller, and some have 

 short stems and a very fern-like appearance, as, for 



