134 



VEGETABLE KINGDOM. 





(Fig. 189). (This mode of growth is in contrast to that which char- 

 acterizes the Endogens.) The flowers exceedingly simple, and the seed 

 naked, — the seed being ordinarily on the inner surface of the scales 

 of cones. Examples are the Pine, Spruce, Hemlock, etc. The name 

 Gymnosperm is from the Greek for naked seed. Gymnosperms in- 

 clude (1) Conifers; (2) Gycads (p. 408). 



Fig. 189-198. 

 191 190 



Plants. — Fig, 189, section of exogenous wood; 190, fibres of ordinary coniferous wood (Pinus 

 Strobus), longitudinal section, showing dots, magnified 300 times; 191, same of the Australian 

 Conifer, Araucaria Cunninghami ; 192, section of endogenous stem. 



Figs. 193 to 198, Diatoms highly magnified ; 193, Pinnularia peregrina, Richmond, Va. ; 194 

 Pleurosigma angulatum, id; 195, Actinoptychussenarius,id;196, Melosira sulcata, id; a, trans- 

 verse section of the same ; 197, Grammatophora marina, from the salt water at Stonington, Conn.; 

 198, Bacillaria paradoxa, West Point. 



The wood of the Conifers is simply woody fibre without ducts, and, 

 in this respect, as well as in the flowers and seed, this tribe shows its 

 inferiority to the following subdivision. The fibre, moreover, may be 

 distinguished, even in petrified specimens, by the dots along the sur- 

 face as seen under a high magnifier. The dots look like holes, though 

 really only thinner spaces. Fig. 190 shows these dots in the Pinus 

 Strobus. In other species, they are less crowded. In one division of 

 the Conifers, called the Araucarice, of much geological interest, these 

 dots on a fibre are alternated (Fig. 191) ; and the Araucarian Conifers 

 may thus be distinguished. 



2. Angiosperms. — Exogens,like the Gymnosperms. Having regu- 

 lar flowers and also covered seed; as the Maple, Elm, Apple, Rose, 

 and most of the ordinary shrubs and trees. Called Angiosperms, be- 

 cause the seeds are in seed-vessels ; and also Dicotyledons, because the 

 seed has two cotyledons or lobes. 



3. Endogens. — Regular flowers and seed ; but growth endogenous, 

 the plants having no bark, and showing, in a transverse section of a 

 trunk, the ends of fibres, and no rings of growth (Fig. 192) : as the 

 Palms, Rattan, Reed, Grasses, Indian Corn, Lily c The Endogens 

 are Monocotyledons ; that is, the seed is undivided, or consists of but 

 one cotyledon. 



Among Algce, three kinds are of prominent interest to the geol- 

 ogist : — 



