r free extremities.

Micheli, of course, discovered the arcyrias, put them in two genera and
several species, which we may only dimly recognize. Persoon first saw
distinctly the outlines of the genus as now understood and adopted the
name given by Hill in his curiously prolix description of certain
species, probably partly of the genus _Arcyria_, partly _Stemonitis_.

=Key to the Species of Arcyria=

_A._ Mature capillitium loosely adhering to the calyculus.

_a._ Mature capillitium far-expanded, drooping.

i. Dusky.

O Long, 12 mm. or more 1. _A. magna_

OO Shorter, about 6 mm. 2. _A. oerstedtii_

ii. Yellow 3. _A. nutans_

_b._ Mature capillitium short, not drooping, though
sometimes procumbent.

i. Capillitium greenish yellow 4. _A. versicolor_

ii. Capillitium reddish, flesh-colored, at
length sordid, etc.

O Capillitium marked by transverse
half-rings, cogs, etc. 5. _A. incarnata_

OO Capillitium marked by sharp-edged
transverse plates and by numerous
nodes 6. _A. nodulosa_

OOO Capillitium marked by close
reticulations 7. _A. ferruginea_

_B._ Capillitium persistently attached to the calyculus.

_a._ Sporangia reddish brown, etc. 8. _A. denudata_

_b._ Sporangia gray or ashen

i. Simple 9. _A. cinerea_

ii. Clustered 10. _A. digitata_

_c._ Sporangia yellow 11. _A. pomiformis_

_d._ Sporangia rose-colored, .5-1.5 mm. 12. _A. insignis_

1. ARCYRIA MAGNA _Rex._

1893. _Arcyria magna_ Rex, _Proc. Phil. Acad._, p. 364.

Sporangia densely aggregated, forming clusters of greater or less
extent, sometimes reaching several centimetres in either direction,
tawny gray or ashen, cylindric, tapering a little above, when expanded
reaching a length of half a centimetre or more, stipitate; peridium
evanescent except the small shallow cup-like base, the calyculus; stipe
long (1 mm.), weak, pale brown or reddish, tubular, the channel filled
with plasmodic masses; capillitiu