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, 

 projecting 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 Galca/rem 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 whit'^ plasmodium of 

 Ghondrioderma MicheUi they appear like crowded glass beads 

 2 /A 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 pui-ple or green, 

 but is generally constant in each species. An exception occurs 

 in Tridiia fallax, 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 a.11 charapters. 

 Diahema depressum has, as a rule, a white plasmodium, but 

 occasionally it is pink. 



De Bary states, that " union never takes pUice between plas- 

 modia of different species," * and my own experience is in accord 



* De Bary, I.e., p. 426. 



