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California Moss eFlora
|Jan 1 2013 ·|
Historically, the majority of the species of the family Polytrichaceae have been apportioned between the two genera Polytrichum (capsules longitudinally ribbed) and Pogonatum (capsules not at all ribbed). As such, the largely tropical and Southern Hemisphere genus Pogonatum has included Polytrichastrum alpinum, as well as Pogonatum contortum and Pogonatum urnigerum. Modern classification stemming in part from the work of Smith (1971) requires attention to additional largely microscopic characters of the sporophyte; and this removes Polytrichastrum alpinum from the genus Pogonatum.
Key to Pogonatum Etc.
In the key that appears below we treat those plants with photosynthetic lamellae so numerous as to cover nearly all the surface of the leaf lamina. The plants here treated have the terminal cell of the photosynthetic lamellae (when viewed in cross-section, marginal when scrapings are viewed) variously ornamented with papillae or cuticular ridges. The plants with numerous photosynthetic lamellae but smooth terminal cells of the lamellae are treated under Polytrichum.
Species included in this key are all in Polytrichaceae:
Meiotrichum lyallii (Mitten) G. L. S. Merrill
Pogonatum contortum (Menzies ex Bridel) Lesquereux
Pogonatum dentatum (Bridel) Bridel, not known from CA
Pogonatum urnigerum (Hedwig) Palisot de Beauvois, not known from CA
Polytrichastrum alpinum (Hedwig) G. L. Smith
At this time, we have verified records of Pogonatum only on the basis of Pogonatum contortum. Pogonatum urnigerum is a common plant on soil banks at high to middle montane elevations in Oregon and farther north even to sea level. Surely, it will eventually be found in California. Pogonatum contortum is restricted to soil bank sites at low to middle elevations in the northwest corner of the state. The photosynthetic lamellae that help to define the family Polytrichaceae are obvious across almost the entire width of the distal portion of the leaf. Pogonatum contortum gets its name from the highly crispate nature of the leaf of the dry plant; and, among Polytrichaceae, it shares that crispate character only with the genus Atrichum, a plant with only a few photosynthetic lamellae restricted in insertion to the area of the costa.
A. Terminal cell of each photosynthetic lamella smooth throughout; plant green and strongly crispate when dry .....Pogonatum contortum
A. Terminal cell of each photosynthetic lamella with obvious papillosity especially on distal end; plant glaucous, not at all crispate when dry .....B
B. Terminal cell of photosynthetic lamellae longer than broad with papillae on that cell rather inconspicuous .....C
B. Terminal cell of photosynthetic lamellae as broad or broader than long with papillae on that cell very conspicuous .....D
C. Excised leaf tending to turn over on its side and to describe 180 degrees of arc when laid on the slide; cells of leaf lamina across the shoulder mostly transversely elongate with transverse walls markedly thicker than lateral walls; outermost walls of terminal cell of photosynthetic lamellae almost as thick as lumen .....Polytrichastrum: P. alpinum
C. Excised leaf tending to lie flat on the slide; cells of leaf lamina across the shoulder mostly quadrate without transverse walls thickening; outermost walls of terminal cell of photosynthetic lamellae rather thin .....Meiotrichum: M. lyallii
D. Terminal cell of photosynthetic lamellae round in section, of same size as adjacent cells of lamellae as seen in lamellar scrape; teeth of leaf margin mostly unicellular; cells hyaline and thin-walled at leaf margin at distal area of leaf base .....Pogonatum urnigerum not known from CA
D. Terminal cell of photosynthetic lamellae distally flat, smaller in longitudinal diameter than adjacent non-terminal lamellar cells as see in lamellar scrape; teeth of margin multicellular; shoulder of leaf without a hyaline border .....Pogonatum dentatum not known from CA
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