MOKPHOLOG Y. 



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



which the pine belongs have 

 naked seeds. For 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 

 Fig. 376. Fig. 377. Finales, but the discovery of 



Spermatozoids of Spermatqzoid of za- the spermatozoids in the pollen 

 zamia in pollen tube; mia showing spiral 

 pg, pollen grain; a, a, row of cilia. (After tube suggests that it IS not 



Webter t0 ) Z idS> (AftCr Webber ' ) closely allied with the Finales, 



and that it represents an order 



coordinate with them. Engler arranges the living gymnosperms somewhat 

 as follows: 



Class Gymnospermae. 



Order i. Cycadales; family Cycadacese. Cycas, Zamia, etc. 

 Order 2. Gingkoales; family Gingkoaceae. Gingko. 

 Order 3. Finales (or Coniferae); family i. Taxacese. Taxus, the common 



yew in the eastern United 

 States, and Torreya, in the 

 western United States, are 

 examples. 



family 2. Pinaceae. Sequoia (redwood of 

 California), firs, spruces, pines, 

 cedars, cypress, etc. 



Order 4. Gnetales. Welwitschia mirabilis, deserts of southwest Africa; 

 Ephedra, deserts of the Mediterranean and of West 

 Asia. Gnetum, climbers (Lianas), from tropical 

 Asia and America. 



