LOWER LAND PLANTS 



159 



mature sporophyte 



sporangium 

 hair-like or 

 cylindrical^ not 

 spherical or 

 oval 



immature sporophyte 



gametophyte with 

 antheridial pits 



Figure 10.2 Anfhoceros, a hornwort or horned liverwort. 



organs; sporophyte with an area of continuous cell 

 division, hence growth, near its base (Figure 10.2). 

 Anthocerotae is distinct from the Class Hepaticae in 

 that the sporophyte is relatively large, persistent, and 

 contains cells with chlorophyll, columella tissue, 

 stomata, and a continuous growth region; sporophyte 

 capsule (sporangium) is wire-like and not distinct 

 from the foot. 



Occurrence: about fifty living species in a single 

 Order Anthocerotales; all tend to be limited to moist 

 soil. 



G.A.\IETOPH">TE 



Structure: membranous; generally a 1 x 1 inch 

 sheet, mostly lobed or divided (often repeatedly equal 

 forking to form extensive masses), with many unicel- 

 lular unbranched "roots" on the under surface; in 

 extensive masses each extreme of a branch or lobe 

 continues to grow; mature gametophytes are near the 

 end opposite the growing end; mature gametophytes 

 generally are dying and sloughing away at a rate 

 approximating that of new growth; dying and slough- 

 ing results in a separation of individuals whenever 

 points of forking are destroyed (a method of asexual 

 reproduction); most species have male and female sex 

 organs embedded within the same gametophyte; in 

 other species sex organs are embedded in separate 

 and slightly different looking male or female gameto- 



phytes. Male sex organs occur singly or grouped on 

 short stalks in chambers within the thallus. Female 

 sex organs occur singly and are not sharply dififer- 

 entiated from the surrounding vegetative tissue of the 

 thallus. 



Reproduction: asexual reproduction mostly by the 

 process of dying and sloughing, but also by formation 

 of marginal thickenings that develop protective cover- 

 ings (product regenerates a new gametophyte); in 

 sexual reproduction sperm form in male sex organs and 

 swim through water to the egg in the female sex 

 organ, fertilization produces a zygote which develops 

 into an embryo sporophyte. 



SPOROPHYTE 



Structure: a basal foot continuous with a 1- or 

 2-inch wire-like capsule (a sporangium); the foot and 

 the base of capsule are in a thin upward extension 

 of the gametophyte. 



In the capsule spores mature from top to bottom; 

 then the capsule splits along one to four "lines," 

 and finally the split capsule parts either separate 

 from the top downward or separate and bow out from 

 a point just below the united tip. 



The foot is a bulb-like structure that anchors the 

 sporophyte to the gametophyte by fitting into a 

 "socket" of the gametophyte. The socket provides a 

 site for the sporophyte to absorb water and nutrients 

 from the gametophyte. 



The horned liverworts, or hornworts, include five 

 or six genera of world-wide plants. However, wher- 

 ever they occur they usually are localized in moist, 

 temperate situations. Normally, they inhabit dis- 

 turbed, acidic soil but they may be found upon rocks 

 or trees. Like liverworts and mosses, they are aflfec- 

 tive in holding moisture and retarding soil erosion. 



Hornworts are unique bryophytes owing to the 

 chlorophyll in their sporophyte. Moreover, their 

 gametophyte often is invaded by blue-green algae, so 

 rather than being green they assume a dark green 

 hue. In addition, they feel greasy. Although some of 

 the blue-green algae are able to fix nitrogen, thus 

 providing nutrients to their horned liverwort hosts, 

 some at least appear to inhibit hornwort growth. 



CLASS HEPATICAE (Liverworts) 



Diagnosis: gametophyte sometimes membranous 

 as in horned liverworts, but mostly leafy; reproductive 

 organs range from partially embedded to stalked; 



