INTRODUCTION. 
7 
plasm, containing numerous nuclei and vacuoles. The latter 
vary in size, and are often seen to contract and discharge their 
contents, which is either watery or contains refuse matter. The 
movements in the interior of the swarm-cell are extended into a 
system of circulation in the plasmodium, which spreads in a net- 
work of veins with a few principal channels. Through these the 
granular substance streams in a rapid torrent which gradually 
comes to a pause in the space of a minute and a half to two 
minutes ; it then immediately reverses its course, maintaining a 
rhythmic flow, backwards and forwards at nearly equal intervals, 
but always of a somewhat longer duration in the direction in 
which the plasmodium is creeping. This movement is continued 
through the smaller veins which branch with increasing intricacy 
till lost in the broad stratum ending at the tumid margin of the 
advancing wave. The whole is invested by a layer of hyaloplasm 
devoid of granular particles, but merging imperceptibly into the 
inner stratum. The hyaloplasm exhibits amoeboid movements, 
pi-ojecting and withdrawing pseudopodia, and is unequal in thick- 
ness over different parts ; it is generally abundant at the advanc- 
ing margin, and a large residuum of substance free from granules 
and charged with refuse matter is left behind, marking the 
track where a plasmodium has passed. The hyaloplasm appears 
to be a more firm condition of the protoplasm assumed when 
exposed on the surface ; how far it may have reference to the 
rhythmic streaming of the plasmodium, or what causes that 
movement, has not been ascertained. 
The description given above applies to plasmodia which creep 
over dead leaves or the surface of logs or woody fungi. Those 
which inhabit the interior of rotten wood usually emerge only at 
the time of fruiting, and then appear as cushion-like masses or 
as scattered globules. The plasmodia of the Calcarece contain 
granules of calcium carbonate (designated " lime "), in addition 
to the protoplasmic particles. The granules vary in abundance 
in different species, being small and inconspicuous under the 
microscope in some, while in the opaque white plasmodium of 
C'honclrioderma Michelii they appear like crowded glass beads 
2 /X or more in diameter, and greatly impede the streaming move- 
ment. The colour varies in different plasmodia ; it is for the 
most part white, yellow, or pink, in some it is pupple or green, 
but is generally constant in each species. An exception occurs 
in I'richia falkix, which usually rises from rotten wood in rosy 
pink globules, but frequently the plasmodium is watery white ; 
the two colours are not met with together in the same growth, 
but the sporangia from each are identical in all characters. 
Dianema depressum has, as a rule, a white plasmodium, but 
occasionally it Ls pink. 
De Bai-y states that " union never takes plfice between plas- 
modia of different species," * and my own experience is in acpoi d 
* De Bary, Lr., p. 420. 
