SPEBMAPBYTES : PH^ENOGAMS. 129 



some of them are very simple. The plants vary extremely in 

 size, the smallest being little floating plants, less than a milli- 

 metre in diameter, while others are gigantic trees, a hundred 

 metres and more in height. 



There are two classes of the spermaphytes : I., the Gym- 

 nosperms, or naked-seeded ones, in which the ovules (macrospo- 

 rangia) are borne upon open carpophylls ; and II., Angiosperms, 

 covered-seeded plants, in which the carpophylls form a closed 

 cavity (ovary) containing the ovules. 



CLASS I. GYMNOSPERMS (Gymnospermce) . 



The most familiar of these plants are the common ever- 

 green trees (conifers), pines, spruces, cedars, etc. A care- 

 ful study of one of these will give a good idea of the most 

 important characteristics of the class, and one of the best 

 for this purpose is the Scotch pine (Pinus sylvestris), which, 

 though a native of Europe, is not infrequently met with 

 in cultivation in America. If this species cannot be had 

 by the student, other pines, or indeed almost any other conifer, 

 will answer. The Scotch pine is a tree of moderate size, sym- 

 metrical in growth when young, with a central main shaft, 

 and circles of branches at regular intervals ; but as it grows 

 older its growth becomes irregular, and the crown is divided 

 into several main branches. 1 The trunk and branches are 

 covered with a rough, scaly bark of a reddish brown color, 

 where it is exposed by the scaling off of the outer layers. 

 Covering the younger branches, but becoming thinner on the 

 older ones, are numerous needle-shaped leaves. These are in 

 pairs, and the base of each pair is surrounded by several dry, 

 blackish scales. Each pair of leaves is really attached to a 

 very short side branch, but this is so short as to make the 



1 In most conifers the symmetrical form of the young tree is maintained 

 as long as the tree lives. 



