Wheldon : Key to the Harpidioid Hypna. 247 



3. Procumbent or ascending, moderately robust, with few rhizoids : 

 leaves strongly plicate, denticulate (4). Prostrate or creeping, in flat 

 patches : under side of stem radiculose (5). 



4. Apices of stems feebly hooked ; leaves only slightly striate 

 (5. uncinata var. abbreviata). Apices strongly hooked : leaves strongly 



plicate, often to base (7). 



6. Leaves large and rather wide, with a very long subule : capsule 

 regular, erect (S. uncinata var. alpina). Leaves moderate (2. 5-3. 5mm.) 

 narrower, subule shorter : capsule oblique, arcuate (5. uncinata var. 

 sueta). 



7. Leaves 3 to 4 mm. long, of which the very long loriform cubule 

 forms about half (8 ) . More slender and delicate : leaves i -3 mm . long (9 ) . 



8. Capsule oblique, arcuate (S. uncinata var. sueta f. plumosa). 

 Capsule cylindrical, erect and symmetrical : pedicels often geminate 

 (S. symmetrica). 



9. Very slender, and creeping, and radiculose throughout : leaves 

 2-3 mm. X .6 mm.: seta short and capsule small (S. uncinata var. 

 plumulosa) . Still smaller, delicate as H. sonimerfeltii, creeping, up to 

 5 cm. long, here and there attached by scattered tufts of radicles : leaves 

 1-2 X .5 mm., plicae and serratures nearly obsolete (S. uncinata var. 

 contigua) . 



(D) Cratoneuron Schimp. 



Erect, ascending or prostrate, usually more or less pinnately branched. 

 Stems clothed with paraphyllia and frequently tomentose. Leaves 

 falcate -secund, base excavate. Tissue usually solid, cells linear, 

 gradually shorter towards leaf base, at decurrent angles suddenly wider, 

 subhexagonal, forming hyaline or coloured auricles. Nerve thick. 

 Dioicous. The British forms consist of one polymorphous species, 

 C. commutatum (Hedw.), which may for convenience be divided into 

 the following subspecies or ' micro -species,' and varieties. 



1. Leaves more or less papillose: stems slender, pinnate, with 

 short subequal hooked branches : perigonial bracts papillose (C. decipiens) . 

 Leaves and bracts never papillose (2). 



2. Very neat and slender: leaves very small, 1.5 mm. long, or 

 shorter (3). More robust : leaves larger, i .5 to 3 mm. long (7). 



3. Plant alpine or subalpine (4). Plant of lower altitudes (6). 



4. Pale yellowish green, to yellowish brown (5). Dark deep green, 

 fuscescent below : straight leaves, 1.5 X 5-. 6 mm. : nerve 49 u. : medium 

 cells 36-38 u., basal about 23 u. long : paraphyllia abundant, and amongst 

 them a few scattered rhizoids (C. gracilentum) . 



5. Paraphyllia many, radicles few or none : leaves ovate rather 

 suddenly or more gradually, tapering, but always wider and shorter 

 than the next : strongly plicate, their texture thin, delicate and trans- 

 lucent, cells short (4-6 times as long as wide) : nerve broad but thin, 

 short, ending at or just beyond mid-leaf (C sulcatum) . Deeper coloured, 

 less pinnate, glossy, paraphyllia and rhizoids few : leaves longer and 

 proportionately narrower, striate (hardly plicate) : cells longer and 

 narrower, less delicate and translucent : nerve more solid, reaching 3/4 

 (C gracilescens) . 



6. Plant of sphagnum moors, slender, soft, 5-10 cm. high : leaves 

 lax, rather long and narrow (1-1.5 mm. long) : alar yellow, translucent, 

 with thin walls : paraphyllia very slender, few, and radicles few and 

 scattered (C. falcatum var. delicatulum) . Plant of shallow sand-dune 

 pools : short (3-5 cm.), yellow or ochreous brown, much branched but 

 hardly pinnate : leaves short and broad (.9-1 mm. long), auricles yellow, 

 opaque, their cell walls incrassate (C. falcatum var. dunale). 



7. Divisions of stem closely and complanately pinnate, pinnae 

 slender : rufous tomentum usually mixed with the abundant paraphyllia : 

 leaves of stem and branches strongly dimorphous : stem leaves from a 



1921 July 1 



