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A Monograph o f the Alyxogastres. 29
I!
MYXOGASTRES (F r ie s ).
My x og a str es, Fries, Syst. Myc., iii. p. 67 (1829); Soliroeter,
K t. FI. Scliles., Vol. iii. p. 98.
M y x om y c e te s , Wallr., FI. Crypt., ii. p. 388 (1 8 3 3 ); Cooke,
Brit. Myx., p. 1 ; R au n k , Myx. Bwil, p. 20; Saoc., Syll., Vol. vii.
pt. i. p. 323.
Mycetozoa, De Bary {Bic Mycctozocn, 1864); Rost. {3Ion.
Sluzowcc) (in part).
PiLZTHlERE, Zopf, in Schenk’s Handh. der Bot., Vol. iii.
(1884) (in part).
Consisting during the entire vegetative period of an accumulation
of naked cells forming a plasmodium possessed of the poioer
of movement, and invested toith an imperfectly differentiated,
yielding membrane. This plasmodium at length becomes transformed
into sporangia containing numerous spm'es which form
a powdery mass at maturity. First, product of spores on
germination either ciliated zoosponxs or amoeboid cells, which
after repeated bipartition and conjugation, combine to form a
plasmodium.
The species are usually aerial, the plasmodium stage being
passed in rotten wood or amongst decaying vegetable matter,
and coming to the surface only to form the sporangia; nevertheless
several species have been observed to pass the whole of
their existence under water. The sequence from the aquatic to
the aerial condition may frequently be seen in the same batch
when developing on logs that are partly submerged.
The most pronounced feature in the evolution of the Myxogastres
is in connection with spore dissemination, and the
following arrangement is based on the relative development of
the capillitium, which is seen in its most perfect form in the genera
Trichia and Areyria. In the Gastromyeetes I have shown elsewhere
’ that the sequence of evolution all tends towards securing
in the most efficient manner, the dissemination of the spores;
commencing with the subterranean genera Fhizopogon and
^ A Monograph of the British Gastroimjcetes. Ann Bot., Vol. iv. pp.
1—103 (4 plates).
Hymenogaster, where the spores are liberated only by the decay
of the plant without any apparent morphological provision for
their dispersion, we trace, as the above ground genera appear,
the gradual evolution of the capillitium through such genera as
Biploderma and Scleroderma, until in Lycoperdon we find the
highly specialized hyphae forming the capillitium effecting at
maturity the rupture of the peridium, and consequent dispersion
of tlie spores. This phase is the most perfect, so long as
dispersion is effected by mechanical methods, but in the Phal-
loiieae we find the mechanical method superseded by a totally
different idea; brilliant colours, usually combined with a strong
odour, and the presence of a sweet substance, bid for the visits
of insects, which in return disperse the spores. In the Myxogastres
the mechanical method of spore dispersion is the most
perfect condition attained, as illustrated by the rough, elastic
capillitium of many species of Areyria. The above allusion
must not he interpreted as implying relationship between the
Gastromyeetes and the Myxogastres ; in fact I see in this point
of agreement no more proof of affinity than exists between the
Phalloideae and those flowering plants that make use of the
same announcements to insects, in the form of colour, scent, and
honey in connection with pollination. I consider the Myxogastres
as illustrating one of the earliest known attempts at
differentiation in the direction that has eventually resulted in
the mass of organisms constituting the vegetable kingdom, but
having originated from the Flagellatae, a group more in touch
with the animal side of life, the work of developing individuality
has been slow, as illustrated by the tardy appearance of cellulose
cell-walls, which, as would be expected, is most complete in
the newly evolved reproductive phase, itself to a great extent
the outcome of a gradual change of environment from aquatic to
aerial—hut the radical mistake, after having adopted the plant
line of development, consisted in the non-development of chromatophores,
and retention of the animal mode of nutrition,
which in the plant world means parasite or saprophyte. The
fungi, a later group, differentiated from ancestors that had
already evolved the leading plant characteristics, including cell