HIGHER LAND PLANTS 



179 



GAMETdPH'iTE 



Slniclure: ranges from a structure with a midrib in 

 the center of a heart or butterfly-shaped membrane 

 having sex organs (reminiscent of certain liverworts 

 and horned liverworts) to both gametophytes being 

 much reduced, without distinct sex organs, and es- 

 sentially within the parental spores (the male game- 

 tophyte forming a resting stage, called a pollen grain 

 and the fertilized female gametophyte becoming part 

 of a seed). 



Reproduction: ranges from conditions similar to 

 other pteridophytes to a complex process involving 

 seed production. 



SPOROPHVTE 



Structure: herbs, shrubs, and trees; leaves simple, 

 compound, or decompound, generally alternate to 

 radiating at the apex of a simple aerial stem; spo- 

 rangia simple to grouped into complex structures. 



Sporangium: ignoring angiosperms, generally upon 

 leaves to associated with modified leaves in the forma- 

 tion of cones; sporangia occur either singly and some- 

 what scattered, characteristically clustered but not 

 fused, fused together into a nut-like structure, or male 

 spore-forming sporangia are grouped into male cones 

 and female spore-forming sporangia are grouped into 

 female cones; see flower organization in Angiosperms. 



Stems: ranging from unbranched to complexly 

 branched rhizomes; to unbranched, equally forked, 

 or irregular branched aerial stems; arranged into 

 nodes and internodes; growth primarily from an 

 apical grovi^h region, but also from axillary buds at 

 the nodes. 



Leaves: simple, compound, or decompound; mar- 

 gins generally pinnatified, also otherwise including 

 entire; arrangements include one or more leaves as 

 the only aerial portion of many plants, leaves alter- 

 nate on aerial stems, or leaves terminal and radiating 

 from the aerial stem apex; basic leaf arrangement is 

 typically alternate; certain leaves become fertile and 

 usually differentiate into hardly leaf-like sporangia- 

 bearing structures that are sometimes organized into 

 separate male and female cones. 



Roots: mostly present; often of a fibrous nature. 



Reproduction: either a single kind of spore is formed 

 and usually develops into a bisexual gametophyte 

 reminiscent of the midribbed liverwort gametophyte; 

 or two kinds of spores are produced, the smaller one 

 developing into a male gametophyte and the larger 



one developing into a female gametophyte; or two 

 kinds of spores are produced, the smaller one develop- 

 ing into a male gametophyte within its spore wall and 

 the larger developing into a female gametophyte 

 within its spore wall, the female gametophyte and 

 spore being involved in seed production (see sperma- 

 tophyte characteristics); also see angiosperms. 



CLASS FILICINEAE (Ferns) 



Diagnosis: known from definite early Lower De- 

 vonian fossils; range in structure from the earliest fos- 

 sils which approximated the psilopsid structure to the 

 complex ferns of today; leaves commonly alternate 

 and pinnatified; stems often entirely underground, a 

 simple or branched rhizome; sporangia mostly upon 

 the undersurface of leaves, but variously distributed; 

 sporangial organization highly variable, primitively 

 occurring singly, now frequently organized into 

 closely set but not fused groups of definite shape 

 (sori) which may have a protective covering (indu- 

 sium) and are upon a specialized raised portion of 

 the leaf (receptable); in Marattiales sporangia are 

 fused (see living psilopsids), and in Marsileales and 

 Salviniales are represented by modified leaves formed 

 into a nut-like structure (sporocarp); spores of one 

 or two kinds, but the two kinds of spores are typically 

 simiter in appearance; both gametophyte and sporo- 

 phyte are functionally independent at maturity; 

 gametophyte small and inconspicuous to minute and 

 approaching being contained within a spore, mostly 

 with chlorophyll and free-living upon the surface of 

 the ground; also free-living but without chlorophyll 

 and underground, some female gametophytes within 

 a female spore and obtain nutrients from spore food 

 reserves (Figure 11.14). 



Occurrence: about 10,000 living species, all but 

 about 260 being true ferns (Order Filicales); mostly 

 in moist, warm, temperate and tropical areas but 

 extending to dry and cold climates as well. 



ORDER OPHIOGLOSSALES (Adder's-tongue and 

 Grope Ferns) 



Diagnosis: indefinite fossil record, Permian (?) to 

 Recent; perennial herbs of small to moderate size, 

 generally in forests or open areas; sporophyte stem 

 short and fleshy, often underground; roots thick and 

 fleshy, mostly simple; leaves simple or pinnately com- 



