. A handbook of cryptogamic botany. Cryptogams. MYXOMYCETES 403 nourishes itself and grows, acquiring, in the case of some Physarese, great dimensions, and forming reticulated masses which may be measured by inches. Fuligo varians (Somm.) (or as it is more commonly called lium septicum (Fr.) or ' ilowers of tan,' from its appearing during summer on tan) is such a body, but the plasmodes of other families of Myxo- mycetes, as well as of some Physarese, generally remain very small in com- parison with this. The appearance of the strands or branches of the plas- mode (under the microscope
. A handbook of cryptogamic botany. Cryptogams. MYXOMYCETES 403 nourishes itself and grows, acquiring, in the case of some Physarese, great dimensions, and forming reticulated masses which may be measured by inches. Fuligo varians (Somm.) (or as it is more commonly called lium septicum (Fr.) or ' ilowers of tan,' from its appearing during summer on tan) is such a body, but the plasmodes of other families of Myxo- mycetes, as well as of some Physarese, generally remain very small in com- parison with this. The appearance of the strands or branches of the plas- mode (under the microscope) is that of a turbid granular mass bordered by a clearer hyaloplasm. The surface of the plasmode of Physarese is in- vested witha soft shiny envelope of a substance different from protoplasm. The plasmodes of certain other forms are similarly invested with en- velopes, as to the nature of which not much is known. The larger portion of the granules contained in the plasmodes of Physarese are of calcium carbonate ; granules contained in other plasmodes require investigation. Nuclei are abundantly present. Many foreign bodies such as spores, diatoms, &c., are often found included in plasmodes. Constant movement is maintained, and the most characteristic is that of the pro- trusion and retraction of pseudopodes. Since protrusion is commonly more active on one side than on the other, an advancing movement of the whole is thus brought about. Internal streamings, more or less copious, answer to the amoeboid movements. The external causes of move- ments are : with reference to (i) illumina- tion, they are negatively heUotropic ; (2) water—they are positively hydrotropic, , when not about to form spores they leave comparatively dry spots and move towards moist places ; {-^ food~-\h&j are positively trophotropic, , they move towards nutrient substances (as might be expected); (4) heat—within certain limits they move towards the warmer side of a surface unequally warm
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