View source for Argyrochosma

{{Treatment/ID
|accepted_name=Argyrochosma
|accepted_authority=(J. Smith) Windham
|publications={{Treatment/Publication
|title=Amer. Fern J.
|place=77: 38. 1987
|year=1987
}}
|basionyms={{Treatment/ID/Basionym
|name=Notholaena sect. Argyrochosma
|authority=J. Smith
|rank=section
|publication_title=J. Bot. (Hooker)
|publication_place=4: 50. 1841
}}
|synonyms=
|hierarchy=Pteridaceae;Argyrochosma
|hierarchy_nav=<div class="higher-taxa"><div class="higher-taxon"><small>family</small>[[Pteridaceae]]</div><div class="higher-taxon"><small>genus</small>[[Argyrochosma]]</div></div>
|etymology=Greek argyros, silver, and chosma, powder, referring to whitish farina covering the abaxial surface of leaf blades in most species
|volume=Volume 2
|mention_page=
|treatment_page=
}}<!--

--><span class="statement" id="st-undefined" data-properties=""><b>Plants </b>usually on rock. <b>Stems</b> compact, erect to ascending, usually unbranched; scales tan to brown, rarely black, concolored, subulate to narrowly lanceolate, margins entire. <b>Leaves</b> monomorphic, clustered, 3–30 cm. <b>Petiole</b> brown or black, rounded, flattened, or with single longitudinal groove adaxially, glabrous except for a few scales near base, with single vascular bundle. <b>Blade</b> lanceolate, ovate, or deltate, 2–6-pinnate, leathery to somewhat herbaceous, abaxially glabrous or covered by whitish farina, adaxially glabrous or sparsely glandular, dull, not striate; rachis straight or flexuous. <b>Ultimate</b> segments of blade stalked or subsessile, usually free from costae, elliptic to ovate or deltate, usually less than 4 mm wide; base often ± cordate, stalks lustrous and dark colored; segment margins plane or often recurved and forming confluent, poorly defined false indusia extending entire length of segment. <b>Veins</b> of ultimate segments free, usually obscure, pinnately branched and divergent distally. <b>False</b> indusia, when present, greenish, narrow, clearly marginal, occasionally concealing sporangia. <b>Sporangia</b> scattered along veins on abaxial leaf surface, often submarginal, containing 64 or 32 spores, usually intermixed with farina-producing glands. <b>Spores</b> brown, tetrahedral-globose, with cristate or rugose surfaces, lacking prominent equatorial ridge. <b>Gametophytes</b> glabrous. <b>x</b> = 27.</span><!--

-->{{Treatment/Body
|distribution=North America;Mexico;West Indies;Central America;South America.
|discussion=<p>The species of <i>Argyrochosma</i> traditionally have been assigned to either <i>Notholaena</i> or <i>Pellaea</i>. Comparative studies (M. D. Windham 1987) have revealed that members of <i>Argyrochosma</i> are not closely related to <i>Notholaena</i> as typified by N. trichomanoides (Linnaeus) Desvaux. The two genera show consistent differences in stem and leaf morphology, sporangial distribution, spore color and ornamentation, chromosome base number, gametophyte morphology, and chemical composition of the farina.</p><!--
--><p><i>Argyrochosma</i> is more closely related to <i>Pellaea</i> (M. D. Windham 1987) and members of these genera are occasionally confused. These two groups are easily distinguished, however, based on the presence or absence of farina, leaf segment size and shape, and characteristics of the stem scales and leaf margins. In addition, all species of <i>Argyrochosma</i> thus far examined have a chromosome number based on x = 27, unique among cheilanthoid ferns. These differences suggest that <i>Argyrochosma</i> is monophyletic and worthy of recognition as a distinct genus.</p><!--
--><p>Species ca. 20 (6 in the flora).</p>
|tables=
|references=
}}<!--

--><div class="treatment-key">
==Key==
<div class="treatment-key-group">
  
{| class="wikitable fna-keytable"
|-id=key-0-1
|1
|Abaxial surfaces of blades glabrous, lacking whitish farina.
|[[#key-0-2| > 2]]
|-id=key-0-1
|1
|Abaxial surfaces of blades obscured by whitish farina.
|[[#key-0-3| > 3]]
|-id=key-0-2
|2
|Ultimate leaf segments articulate, dark color of stalks stopping abruptly at segment bases; rachises flattened or shallowly grooved adaxially; margins of fertile ultimate segments usually revolute, often concealing mature sporangia.
|[[Argyrochosma microphylla|Argyrochosma microphylla]]
|-id=key-0-2
|2
|Ultimate leaf segments not articulate, dark color of stalks continuing into segment bases abaxially; rachises rounded adaxially; margins of fertile ultimate segments plane to somewhat recurved, not concealing mature sporangia.
|[[Argyrochosma jonesii|Argyrochosma jonesii]]
|-id=key-0-3
|3
|Ultimate leaf segments articulate, dark color of stalks stopping abruptly at segment bases; margins of ultimate segments plane, not recurved or revolute; sporangia following secondary veins for most of length.
|[[Argyrochosma incana|Argyrochosma incana]]
|-id=key-0-3
|3
|Ultimate leaf segments not articulate, dark color of stalks continuing into segment bases abaxially; margins of ultimate segments usually recurved or revolute; sporangia following secondary veins for short distance near segment margin.
|[[#key-0-4| > 4]]
|-id=key-0-4
|4
|Pinna costae distinctly flexuous; branches arising from prominent angles.
|[[Argyrochosma fendleri|Argyrochosma fendleri]]
|-id=key-0-4
|4
|Pinna costae straight or nearly so; branches not arising from prominent angles.
|[[#key-0-5| > 5]]
|-id=key-0-5
|5
|Petioles chestnut brown, 0.50–0.75 mm diam.; blades somewhat herbaceous; veins often visible adaxially; sporangia containing 64 spores.
|[[Argyrochosma dealbata|Argyrochosma dealbata]]
|-id=key-0-5
|5
|Petioles reddish brown to black, usually more than 0.75 mm diam.; blades leathery; veins obscure; sporangia containing 32 spores.
|[[Argyrochosma limitanea|Argyrochosma limitanea]]
|}
</div></div><!--

-->{{#Taxon:
name=Argyrochosma
|author=Michael D. Windham
|authority=(J. Smith) Windham
|rank=genus
|parent rank=family
|synonyms=
|basionyms=Notholaena sect. Argyrochosma
|family=Pteridaceae
|distribution=North America;Mexico;West Indies;Central America;South America.
|reference=None
|publication title=Amer. Fern J.
|publication year=1987
|special status=
|source xml=https://jpend@bitbucket.org/aafc-mbb/fna-data-curation.git/src/eaa6e58056e40c9ef614d8f47aea294977a1a5e9/coarse_grained_fna_xml/V2/V2_89.xml
|genus=Argyrochosma
}}<!--

-->[[Category:Treatment]][[Category:Pteridaceae]]