loped by repeated
lateral and apical branching of the columella, at length assuming at the
surface the form of a distinct net which supports an evanescent
peridium.

The genus is marked by its surface-net supported at the tips of the
dichotomously branched divisions of the columella. Over the net is
spread, theoretically at least, the peridial film supported by very
short points projecting from the net,--the peridial processes; the
peridium, however, is seldom seen; in some cases, certainly, is never
developed. Rostafinski first defined the genus as employed by recent
writers. Gleditsch simply renamed Micheli's _Clathroidastrum_; all
writers subsequent included species of other genera.

The taxonomy of this genus is of the most difficult. Macroscopic,
defining characters are few, and even these sometimes uncertain.
Microscopic distinctions also tend to be illusive, variable in such
fashion that often at the critical point the most exact description
fails. All that may be done at present is to recognize two or three
definite types and then cautiously differentiate among these with the
light we have, until more general study of the group brings to service a
wider range of observation with more comprehensive record on which
judgment may better be sustained.

We have before us many and beautiful forms of this genus yet unstudied.
Some of these doubtless have already found place in our growing
taxonomic literature; some apparently undescribed; all to wait wider
leisure or perhaps a younger hand.

The entire life-history of every form is none too much if we would set
out with any hope of accuracy the genetic relationships for which
taxonomy stands. Recently European students are making the color of the
plasmodium a basis for species-discrimination, which is good so far. But
plasmodic characters are at present unserviceable generally, for two
reasons; they vary in the same species; and unfortunately, when most
needed, they are unknown and inaccessible. The student is generally
confronted by forms mature, the plasmodic stage already past.

=Key to the Species of Stemonitis=

_A._ Sporangia connately united.

_a._ Spores verruculose 1. _S. confluens_

_b._ Spores reticulate 2. _S. trechispora_

_B._ Sporangia at maturity distinct.

_a._ Spore-mass grayish black.

1. Larger, 8-12 mm. spores distinctly
reticulate or warte