3>6 



MORPHOLOGY. 



Fig. ,176. 

 Spermatoz lids of 

 zamia in pollen tube; 

 pg, pollen grain; a, a, 

 spermatozoids. (After 

 Webber.) 



Order i 

 Order 2 

 Order 3 



Fig. 377- 

 Sperniatozoid of za- 

 mia showing spiral 

 row of cilia. (After 

 Webber.) 



are exposed on the outer surface. All the plants of the great group to 



which the pine belongs have 

 naked seeds. P'or this reason 

 the name ^' gymnosperms^^ 

 has been given to this great 

 group. 



637. Classification of gymno- 

 sperms. — The gingko tree has 

 until recently been placed with 

 the pines, yew, etc., in the order 

 Finales, but the discovery of 

 the spermatozoids in the pollen 

 tube suggests that it is not 

 closely allied with the Pinales, 

 and that it represents an order 



coordinate with them. Engler arranges the living gymnosperms somewhat 



as follows: 



Class Gymnospermae. 



Cycadales; family Cycadacea:. Cycas, Zamia, etc. 

 Gingkoalcs; family Oingkoacerc. Gingko. 



Pinales (or Coniferce); family I. Taxaceae. Taxus, the common 



yew in the eastern United 

 States, and Torreya, in the 

 western United States, are 

 examples, 

 family 2. Pinace:e. Sequoia (redwood of 

 California), firs, spruces, pines, 

 cedars, c\'press, etc. 

 Welwitschia mira bills, deserts of south^\■est Africa; 

 Ephedra, deserts of the Mediterranean and of \\>st 

 Asia. Gnetum, climbers (Lianas), from tropical 

 Asia and America. 



Order 4. Gnetales. 



