206 THALLOPHYTA. [CH. 



distinct traces of original or secondary cell-contents in well 

 preserved petrified plant-tissues. There is often a difficulty, 

 however, in distinguishing between the true cell-contents and 

 the cells of some parasitic or saprophytic intruder. In some 

 petrified corky tissue in a silicified nodule from the Permo- 

 Carboniferous beds of Autun, Renault has recently discovered 

 what he believes to be traces of a Myxomycetous plasmodium. 

 The cork-cells would be without protoplasmic contents of their 

 own, and their cavities contain a number of fine strands 

 stretching from the cell-walls in different directions and uniting 

 in places as irregular or more or less spherical masses. The 

 drawings given by Renault of these irregular reticulated struc- 

 tures with scattered patches of what may possibly be petrified 

 plasmodial protoplasm bear a striking resemblance to the plas- 

 modium of a Myxomycete. A figure of the capillitium of a species 

 of Leocarpus figured by Schroter^ in his account of the Myxo- 

 mycetes in Engler and Prantl's work is very similar to that of 

 Renault's * plasmodium.' 



It is by no means inconceivable that the Myxomycetes 

 Mangini may be correctly referred to this group, but the wisdom 

 of assigning a name to such structures may well be questioned. 



The other two examples call for little notice. Messrs Cash 

 and Hick^ in a paper on fossil fungi from the Coal-Measures 

 refer to some small spherical bodies as possibly the spores of a 

 Myxomycete. They might be referred equally well to numerous 

 other organisms. 



Goppert and Menge^ in their monograph on plants in the 

 Baltic Tertiary Amber, express the opinion that an ill-defined 

 tangle of threads which they figure may be a Myxomycete. 



It would serve no useful purpose to quote other instances 

 of possible representatives of fossil Mycetozoa; but the con- 

 sideration of the above examples may serve to emphasize the 

 desirability of refraining from converting a possibility into an 

 apparently recognised fact by the application of definite generic 

 and specific names. 



1 Schroter (89) p. 32, fig. 18 B. 



2 Cash and Hick (782) pj^ yj, gg^ 3, 



3 Goppert and Menge (83) PI. xiii. fig. 106. 



