172 



PHYLUM TRACHEOPHYTA: 



extension of the midrib causing a blunt point at the 

 apex; cuspidate, apex extension tooth-like; aristale, 

 like mucronate, but extension is longer and sharper to 

 hair-like; truncate, appearing to be cut off squarely; 

 retuse, apex with a shallow notch; emarginate, apex 

 with a well-defined noicYi; falcate , apex curving, sickle- 

 shaped; and circinate, falcate-like tip almost forms a 

 complete circle. 



The following organizations or modifications of leaves 

 are of importance in identification: peltate, a leaf in 

 which the petiole is inserted to some part of the lower 

 surface of the blade rather than to the blade base or 

 margin; perfoliate, an organization where the leaf 

 blade entirely surrounds a stem; connate-perfoliate, 

 where two leaf bases are joined together in such a 

 manner as to surround a stem; sessile leaf, one with- 

 out a petiole, typical of perfoliate, connate-perfoli- 

 ate, clasping, and certain other leaves; clasping leaf, 

 the base of a sessile leaf blade is inserted and extends 

 only partly around a stem; rachis, leaf without a 

 blade, the petiole (phyllode) and perhaps the stipules 

 constituting the leaf; and spine, generally a sharply 

 pointed rachis, a modified leaf and not a modified 

 stem, or thorn. 



PTEWDOPHYTES (Fern Plants) 



Some botanists consider Tracheophyta to include 

 two phyla, the fern plants, Pteridophyta, and seed 

 plants, Spermatophyta. Although such a grouping 

 no longer emphasizes apparent phylogeny because 

 each group probably does not trace back to a com- 

 mon ancestor, the terms still are useful. The pterido- 

 phytes include those tracheophytes that do not form 

 seeds. Therefore, the fern plants include three sub- 

 phyla, Psilopsida, Lycopsida, and Sphenopsida, plus 

 one class (Filicineae) of the Subphylum Pteropsida. 

 The spermatophytes include the four remaining 

 classes of Pteropsida, the Cycadae, Ginkgoae, Conil- 

 erae, and Angiospermae. 



The pteridophytes are further characterized as 

 follows: 



Diagnosis: generally moss-like or fern-like; leaves 

 either without veins, with a single vein (leaves 

 called microphylls), or with branched veins (mega- 

 phylls); stem and root development poor to mod- 

 erately complex, an underground stem (rhizome) 

 usually is present; sporangia produce one or two 



kinds of spores; when two spores are formed, smaller 

 ones produce male gametophytes but are not modi- 

 fied as pollen grains and larger spores produce fe- 

 male gametophytes but are not involved in ovule or 

 seed formation; sperm is formed and released from a 

 male sex organ, fertilization commonly features 

 flagellate sperm moving through water to the female 

 sex organ, a zygote forms in the female gametophyte, 

 the sporophyte embryo develops, and the sporophyte 

 normally matures without a resting stage; the pri- 

 mary means of fern plant diagnosis is the lack of seed 

 production. 



Subphylum PSILOPSIDA (Whisk Ferns, etc.) 



Diagnosis: known from Silurian to Recent; 

 perennial herbs mostly to about three feet tall, 

 shrubby and erect or grow upon plants and hang 

 downward; sporophyte with simple organs, with or 

 without leaves, with a branching aerial stem and an 

 underground stem (rhizome), rhizome generally giv- 

 ing rise to multicellular filaments; roots are absent; 

 leaves when present often lack veins, are small and 

 arranged alternately along stems; sporophyte organs 

 typically have veins throughout; spore-forming or- 

 gans (sporangia) are at the apex of minute branches; 

 spores of one type; both sporophyte and gametophyte 

 are functionally independent at maturity; living 

 gametophytes inconspicuous, ordinarily a branched 

 cylindrical structure containing multicellular sex 

 organs on the same plant (Figure 11.5). 



Occurrence: three living species: Tmesipteris tan- 

 nensis, either hanging from other plants (mostly on 

 tree ferns), or a ground form in deep humus is leaved, 

 2 to 10 inches long, and is found in Australia, New 

 Zealand, and the adjacent South Pacific islands. 

 Psilotum nudum and P. faccidiim, the whisk ferns, are 

 sparsely leaved subtropical to tropical plants of both 

 hemispheres and either are upon tree ferns or coco- 

 nuts, are found in soil under trees, or are found upon 

 rocks and even on open ground. The whisk ferns may 

 be dwarfed and only 2 to 3 inches high, or may attain 

 their full growth of 30 to 40 inches. Only P. nudum 

 enters the United States, and only in the state of 

 Florida. 



GAMETOPinTE 



Structure: unknown in fossils; living forms small, 

 up to about 1 inch long; commonly are equally fork- 

 ing or irregularly branching cylinders that resemble 



