rhizopods outside the vegetable and in the animal kingdom, and this is
undoubtedly the true position for the amoebae, which are their earlier
and simpler forms, the Mycetozoa, which _may_ be directly derived from
the same stem, are at least brought very near to the domain of zoology."

Notwithstanding all the controversy in regard to the matter, the study
of the slime-moulds still rests chiefly with the botanists. A simple
phylogenetic scheme for thallophytes is offered in the Strasburger text
as follows:--

THALLOPHYTA

1. SCHIZOPHYTA
BACTERIA
CYANOPHYCEAE

2. FLAGELLATA
{ MYXOMYCETES
{ PERIDINEAE
_a_ { CONJUGATAE
{ HETEROCONTAE

{ CHLOROPHYCEAE
_b_ { CHARACEAE

3. RHODOPHYCEAE

4. FUNGI

About 500 species of slime-moulds have been described. Saccardo
enumerates 443, inclusive of those denominated doubtful or less
perfectly known. These 443 species are distributed among 47 genera, of
which 15 are represented by but a single species each,--monotypic. In
the United States there have been recognized about 300 species. Of those
here described, some are almost world-wide in their distribution, others
are limited to comparatively narrow boundaries. The greater number occur
in the temperate regions of the earth, although many are reported from
the tropics, and some even from the arctic zone. Schroeter found
_Physarum cinereum_ at North Cape. Our Iowa forms are much more numerous
in the eastern, that is, the wooded regions of the state. _Physarum
cinereum_ has however been taken on the untouched prairie, and on the
western deserts, as also _Physarum contextum_ on the decaying stem of
_Calamagrostis_, far from forest.

As to the economic importance of our myxomycetes, there is no long
chapter to write. Fries says: "Usu in vita communi parum admodum sese
commendant, sed in oeconomia naturae certe non spernendi. Multa
insectorum genera ex eorum sporidiis unica capiunt nutrimenta." However
this may be, there is one species which has come to light since Fries's
day which is the source of no inconsiderable mischief to the
agriculturist. _Plasmodiophora brassicae_ occasions the disease known as
"club-root" in cabbage, and has been often made the subject of
discussion in our agricultural and botanical journals.[13] Aside from
the injurious tendencies, possible or real, of the forms mentioned, I
know not that all