HIGHER LAND PLANTS 



177 



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Rgure 11.10 Club moss, tycopod/um, types. Left, L iucidulum (x 'j) 

 with enlarged sporangium-bearing and vegetative leaves. Right, I. 

 obscurum {x ' ■_i) with enlarged sporangium-bearing and vegetative 

 leaves. (Used by permission, from Arthur Cronquist, Introductory 

 Botany, Harper, New York, 1961.) 



GAMETOPHYTE 



Structure: Eqmsetum is minute to (rarely) 1 inch, 

 generally on damp ground, and contains chlorophyll; 

 mature plant an irregular cushion-shaped structure 

 attached to the substrate by "hairs"; sex organs 

 multicellular and similar to those in the quillworts 

 (Isoetales). 



Reproduction: similar to other pteridophytes; ga- 

 metophyte after a period also dying and decaying. 



SPOROPll^TE 



Structure: many fossil trees with large and some- 

 times branched leaves; living species herbaceous to 

 shrubby, surface tissues often containing silica (once 

 used for scouring), mostly under 3 feet, South Amer- 

 ican vine to 36 feet; composed of finely grooved. 



jointed stems, whorled leaves (living forms micro- 

 phylls), and roots originating from underground 

 stems (rhizomes); sporangia on specialized stalks, 

 stalk apex organized into a cone; details to emphasize 

 Equisetum. 



Sporangium: many sporangia are on each cone 

 scale, and the cone scales are grouped into closely set 

 whorls upon a central axis, to form a cone at the end 

 of the axis; the axis is on a vegetative stem or a 

 strictly fertile, non-chlorophyllous stem arising from 

 a rhizome. 



Stems: simple or branched, green, and photo- 

 synthetic; unique in having whorls of branches origi- 

 nate from the nodes, distinct joints at the nodes (the 

 internodes being elongate and ribbed or longitudi- 

 nally grooved) ; and a constantly growing base of each 

 node which allows disjointing at the nodes; stem 

 anatomy, especially vein organization, is unique. 



Leaves: whorled, arising from joints, or nodes, and 

 aligning with an underlying internodal rib; typically 

 are narrow, less than an inch long, have a single un- 

 branched midvein (microphylls), have generalized 

 structure but little or no chlorophyll, and have the 

 lateral margins of adjacent leaves fused except at the 

 tips; a ring of fused leaves forms a protective leaf 

 sheath around each stem joint (a growing part of the 

 stem); leaves often were more generalized in fossil 

 species; microphylls, except in a few fossil forms. 



Roots: originate at the nodes of an underground 



ANTHERIDIUM 



SPORO- 

 PHYTE 



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Figure IV.ll Life cycle of Lycopodium, a club moss: e., egg; e.s., 

 embryo sporophyte; s., sperm; z., zygote. (Used by permission, from 

 Arthur Cronquist, Iniroductory Botany, Harper, New York, 1961.) 



