The Plani Kingdom - 613 



Carboniferous period, indeed, some Lycop- 

 sida achieved the form of gigantic trees (see 

 Fig. 29-13). Moreover, it is known that accu- 

 mulated masses of these large Lycopsida gave 

 rise to most of the present-day huge deposits 

 of coal. 



Today the Lycopsida have diminished to 

 just four genera (about 900 species) of small 

 (usually less than 1-foot-tall) relatively unim- 

 portant plants. These include the club 

 mosses (Fig. 31-20) and the quilbvorts. 



The Lycopsida, like other Tracheophyta, 

 have a dominant sporophyte generation, by 

 which the species is commonly identified 

 (Fig. 31-20). But the gametophyte, typically, 

 takes the form of a semimicroscopic, color- 

 less, subterranean thallus, such as is shown in 

 Figure 31-21. Lycopsidan sporophytes, on the 



ANTHERIDIUM 

 EMBRYO 



Fig. 31-20. Modern lycopsidans are rather small pros- 

 trate plants, such as this club moss (Lycopodium c/ava- 

 tum). These plants also may be called "creeping 

 ground pines." Note the dichotomous branching of 

 the stem and the conelike spore-bearing structures. 

 (From The Plant World.) 



ARCHEGONIUM 



EGG 



SHIZOID 



Fig. 31-21. The haploid gametophyte generation of 

 Lycopodium. This small sexual form of the plant, which 

 is less than V2 inch long, lives almost completely buried 

 on the surface of the soil. The fertilized egg, how- 

 ever, gives rise to the larger dominant diploid sporo- 

 phyte (Fig. 31-20) as in all of the higher plants (Tra- 

 cheophyta). 



other hand, display well-differentiated vas- 

 cular tissues (both xylem and phloem); and 

 they have very good root, stem, and leaf sys- 

 tems. The roots and stems tend to branch 

 dichotomously (by successively forking into 

 two more or less equal branches) as growth 

 occurs. The leaves tend to be small and to 

 come off the stem in circlets at regular inter- 

 vals (giving the plant a "mossy" appearance); 

 and the spore-bearing leaves (sporophylls) 

 tend to be clustered into elongate club-shaped 

 conelike structures (see Fig. 31-20). 



Several club mosses belonging to the genus 

 Lycopodium (Fig. 31-20) are commonly called 

 creeping ground pines, and frequently these 

 are employed as decorative material at 

 Christmas time. Such species display an 



