3IO CLASSIFICATION 



Nat. Order 3. Gnetacece. — This differs very much in 

 habit from the Pines (Coniferce). Gnetum and Ephedra 

 are two important genera. The Gnetum are climb- 

 ing shrubs or erect trees with jointed stems, opposite 

 shining entire leaves, and axillary or terminal spikes 

 of verticillate monoecious or dioecious flowers. The 

 Ephedra are leafless, much-branched shrubs growing 

 in desert regions of the Temperate Zones. Associated 

 with them is Welwitschia mirabilis, a most extra- 

 ordinary and anomalous dwarf tree of South Africa, 

 which attains a great age. It has a table-like trunk 

 4 to 5 feet in diameter, seldom raised more than 6 

 to 12 inches above the, ground, bearing a single pair 

 of leaves about 6 feet long, persisting throughout the 

 life of the plant, and believed to be the first pair of 

 leaves or cotyledons. When old, these leaves split 

 into numerous strips, which lie stretched upon the 

 ground. 



Coniferce, Cycadacece, and Gnetacece are anemo- 

 philous. The male flowers form a large quantity of 

 very light, dry, mealy pollen, sometimes especially 

 adapted for wind-transport by appendages resembling 

 little bladders filled with air. The pollen is so abun- 

 dant that in Pine-woods the pollen is often carried, 

 some distance by the wind, and when washed to the 

 ground by rain produces the phenomena known as 

 "Sulphur showers". In all the families the micro- 

 pyle of the naked ovule secretes a drop of liquid 

 during pollination, which catches the pollen grains 

 brought by the wind and draws them into the micro- 

 pyle as it dries up. 



