12 HISTORICAL GEOLOGY 



forests, especially of the great Coal (Pennsylvanian) age. (1) Ly co- 

 pods usually have branching stems upon which are crowded 

 numerous small, single-nerved, needle-like leaves. Modern repre- 

 sentatives are the small "Ground-pines" or "Club-mosses" 

 so familiar as Christmas decorations. (2) Equisetce have erect 

 growth, hollow or pithy segmented stems, and leaves arranged in 

 whorls around the stems. (Fig. 101.) Modern representatives 

 are the "Horse-tails," which are rush-like plants often seen along 

 our streams. Both Lycopods and Equisetse grew to be large trees 

 during the great Coal (Pennsjdvanian) age. (3) Filices or Ferns 

 of temperate climates usually have fronds springing from a buried 

 stem, while tropical forms may have fronds arranged around the 

 summit of tree-like trunks. 



Cycadofilices are fern-like plants (Fig. 102) which have been 

 recently recognized as a group seemingly intermediate between the 

 highest Cryptogams (i.e. Filices) and the lowest Phanerogams 

 (i.e. Cycads). They possess seeds but not true flowers, and show 

 certain other characters intermediate between Ferns and Cycads. 

 These plants are all extinct, but from the fossil and evolution stand- 

 points they are important. 



II. Phanerogams comprise the seed-bearing, flowering plants 

 whose reproductive organs are stamens and pistils and whose seeds 

 contain embryo plants. 



1. Gymnosperms or the so-called "naked seed" plants include 

 all those which do not have their seeds inclosed in a case or ovary. 

 They possess very simple flowers, and their mode of growth is 

 exogenous. 1 (1) Cycads are palm-like in appearance (Fig. 135), 

 certain of them being erroneously called "Sago Palms." True 

 Palms, however, are Angiosperms with endogenous growth. In 

 some waj^s Cycads also resemble the Ferns. Though now un- 

 common, the Cj^cads are of considerable geological importance. 

 (2) Cordaites (Fig. 103) are now entirely extinct, but during the 

 latter part of the Paleozoic era they grew extensively as tall, slender 

 trees "with trunks rising to great height before branching, and 

 bearing at the top a dense crown, composed of branches of various 

 orders, on which simple leaves of large size were produced in abun- 



1 Exogenous plants grow from without; have distinct bark, wood, and 

 pith; and show concentric rings of growth, a new ring usually being added 

 each year. Endogenous plants grow from within and have neither pith nor 

 concentric rings of growth. 



