SPEEMAPH TTES : PHJZNOGAMS. 



141 



to the second order, but representatives of the others are 

 found in the southern and southwestern states. 



The cycads are palm-like forms having a single trunk 

 crowned by a circle of compound leaves. Several species are 

 grown for ornament in conservatories, and a few species occur 

 native in Florida, but otherwise do not occur within our limits. 



The spore-bearing leaves usually form cones, recalling some- 



FIG. 78. Illustrations of gymnosperms. A, fruiting leaf of a cycad (Cycas), 

 with macrosporangia (ovules) (ou.), x y 4 . B, leaf of Gingko, x y 2 . C, branch 

 of hemlock (Tsuc/a), with a ripe cone, x 1. D, red cedar (Juniperus), x 1. 

 E, Arbor-vitsB ( Thuja) , x 1. 



what in structure those of the horse-tails, but one of the com- 

 monest cultivated species (Cycas revoluta) bears the ovules, 

 which are very large, upon leaves that are in shape much like 

 the ordinary ones (Fig. 78, A). 



Of the conifers, there are numerous familiar forms, including 

 all our common evergreen trees. There are two sub-orders, 

 the true conifers and the yews. In the latter there is no true 



