SLIME MOULDS (mYXOMYCETES) . II 



spores fill the infested host cells. Two species have been described. 

 The nature of Ph. leguminosanim is doubtful, as it may have been 

 •confused with one of the stages of the nodule-producing bacteria, 

 which are found in the roots of leguminous plants. 



The parasitic slime mould, Tetramyxa, occurs as one described 

 species Tetramyxa parasitica, which lives in the stems and flower stalks 

 of water plants, as Ruppia rostellata, where it causes tubercles 0.5 to 

 I mm. in diameter. Each host cell contains numerous colorless spores 

 united into tetrads. 



SorosphcBra is represented in Germany by S. veronica; found in the 

 stems and petioles of Veronica hederifolia, V. triphylla and V. chamce- 

 drys. The cells of the galls are swollen and filled with numerous 

 spheric or ellipsoidal brown balls, 15 to 22 /x in diameter, formed of a 

 single layer of spores united into a hollow sphere and covered externally 

 by their pellicle. 



ORDER III. MYXOGASTRALES.— This order includes the true 

 slime moulds which are non-parasitic, but live on decaying organic 

 material, such as old logs, leaf mould in the forest, compost heaps, 

 spent tan bark and other organic debris in the fields, woods, and 

 along the roadsides. One form grows over the grass of lawns and 

 smothers the grass with its plasmodium and later by its sporangia and 

 spores. The plasmodium is a naked mass of protoplasm usually of a 

 reticulate structure and multinucleate. It arises by the union of the 

 myxamoeba which are developed from the flagellate myxomonads by 

 the loss of the vibratile flagella. Such a plasmodium is known as a 

 fusion Plasmodium.^ It usually assumes a reticulate, or net-like, 

 structure and currents of protoplasm are seen flowing along the strands 

 of greater or less thickness of which the plasmodium is composed. The 

 central portion of each current is denser and moves more rapidly than 

 the marginal clearer protoplasm. Perhaps we are justified in stating 

 that the outer protoplasm is the ectoplasm and the inner granular 

 cytoplasm containing food substances and other included substances 

 is the endoplasm. For some time the plasmodium may flow in a given 

 direction and later it may reverse its course, moving in an entirely 

 opposite direction. The color of the plasmodium difi"ers in different 

 species, as the following table will show. White or yellow seem to be 

 the more usual colors. 



1 In Lahyrinlhiila Cicnkowskii parasitic in Vauchcria the plasmodium is filamen- 

 ous. 



