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IV. MUSCI. 
\_Hypnum. 
One of the largest genera of mosses, found in all parts of the globe. The species are 
extremely difficult of discrimination. Considerable experience and proficiency are required 
before a beginner can name any of the species correctly. Most of the New Zealand ones 
are referred to Stereodon by Mitten, but I have iu this genus as in others followed Wilson’s 
and my own generic nomenclature, as given in the Flora of New Zealand, being convinced 
that it is on the whole the best for a local flora ; there are however no limits to the discre- 
pancies of opinion as to the system and nomenclature of the pleurocarpous mosses, and as 
to which the highest authorities are completely at issue. The groups here adopted are pretty 
natural, but it is not always easy to perceive the characters upon which they are fouuded, 
especially those of the secund-leaved group ( Cupressformia ), to which so many species 
belong. 
KEY TO THE GROUPS AND SFECIES OF HYPNUM. 
I. Stem and branches covered with matted radicles amongst the leaves. 
A. Tamariscina. Leaves small. Nerve strong. Fruitstalk smooth. 
II. Stem and branches not covered with radicles. 
a. Leaves imbricate all round the stem , squarrose or erect or incurved , or secund or 
falcate, not 2-fariotts or distichous. 
* Leaves more or less falcate and secund , often circinate. 
B. Adunca. Stems flaccid. Operculum short, conic. 
C. Hispida. Stems elongate, rigid. Nerve very strong. Operculum beaked. 
D. Cupressiformia. Stem flaccid. Nerve 0 or short and slender. Operculum beaked. 
** Leaves spreading, not squarrose nor large nor concave. 
E. Prolonga. Fruitstalk scabrid. Operculum beaked. 
F. Conferta. F'ruitstalk smooth. Operculum beaked. 
G. Rutabula. Fruitstalk scabrid. Operculum conic. 
H. Serpentia. Fruitstalk smooth. Operculum conic. 
*** Leaves squarrose and spreading , large and often concave. 
I. Stellata. Capsule not grooved. 
J. Ptychomnion. Capsule grooved. 
**** Leaves closely imbricate , not squarrose , large and concave. 
K. Cochlearifolia. 
/B. Stems compressed. Leaves imbricate, the lateral spreading 2-fariously. 
L. Distich ophylla. 
A. Tamariscina. — Stems pinnately or 2-pinnatety branched, covered with matted 
green, fibri/lous rootlets. Leaves imbricated alt round the stems and branches, not 2- 
farious or distichous ; nerve stout. 
* Stems procumbent, straight or slightly arcuate. 
Stems pinnately branched ; branches irregular in length. Leaves 
not plaited; perichaetial with few cilia 1. H. furfurosum. 
Stems pinnately branched ; branches short, close-set, regular. Leaves 
plaited; perichaetial with many cilia 2. H . fulvastrum. 
Stems 2-pinnately branched 3. II. sparsum. 
** Stems very arcuate, proliferous from the descending assurgent apices, 2-pinnate. 
Leaves of branches incurved ; nerve prominent below the apex on 
the back 4 . H. hzviusculum. 
Leaves of branches with erect apices ; nerve not prominent ... 5. H. denticulosum. 
B. Adunca. — Leaves falcate , secund; nerve single, continuous or vanishing below the 
apex. Fruitstalk smooth. Operculum short, conical ( unknown in H. limbatum). Often 
aquatic or marsh mosses. 
