verse to the sporangial
cavity, attached usually at each end, plain or
only slightly roughened _Dianemaceae_

_B._ Capillitium plain, papillose, or spinulose, often
scanty, not netted, the threads sometimes
attached by one end to the sporangium wall _Perichaenaceae_

_C._ Capillitium a distinct net, usually attached
below to the sporangial wall; sculpture
various, not continuous spiral bands _Arcyriaceae_

_D._ Capillitial threads transverse, fascicled,
attached at both ends, but sculptured by well
defined spiral bands _Prototrichiaceae_

_E._ Capillitial threads typically free, sometimes
more or less branched, forming a loose net
attached below, characterized by definite
spiral bands, or sometimes by scattered rings _Trichiaceae_

_A._ DIANEMACEAE

=Key to the Genera of the Dianemaceae=

_A._ Capillitial threads attached at one end, or free 1. MARGARITA

_B._ Capillitial threads attached at each end 2. DIANEMA

=1. Margarita= _List._

1894. _Margarita_ Lister, _Mycet._, p. 203.

Sporangia sessile, the capillitium simple, hair-like, coiled.

1. MARGARITA METALLICA (_Berk. & Br._) _List._

PLATE XVII., Figs. 1, 1 _a_, 1 _b_.

1838. _Physarum metallicum_ Berk. & Br., _Mag. Zool. & Bot._, I.,
p. 49.

Sporangia scattered or clustered, globose, or somewhat plasmodiocarpous,
.5-1 mm., sessile, coppery iridescent, the peridium thin, opening above
irregularly; capillitium of long flexuous, coiling, simple or little
dividing threads, nearly smooth, with infrequent attachments to the
peridial wall; spores in mass yellowish, transparent under the lens,
delicately verruculose, 10-12 mu.

One of the handsomer species of the present group. So far a Pacific
coast form. California, Oregon, Washington; reported from Chile.

=Dianema= _Rex_

1891. _Dianema harveyi_ Rex, _Proc. Phil. Acad._, p. 397.

Sporangia simple or plasmodiocarpous; capillitium composed of threads
without characteristic thickenings running entirely across the
sporangium attached both to the base and to the opposite wall, not
joined to form a network.

=Key to Species of Dianema=

_A._ Sporangia distinct, iridescent 1. _D. harveyi_

_B._ Fructification more or less plasmodiocarpous,
d