282 



STRUCTURAL BOTANY 



mycetes generally have this power, but in most cases they 

 live on dead and decaying substances, such as fragments of 

 bark and wood. Our type is exceptional in preying on 

 living tissues. Its frequency in any particular season 

 depends on the abundance of the Fungi which it feeds on. 

 The plasmodium contains an immense number of 

 nuclei, which are only absent from the clear external 



portion. The nuclei (see Fig. 

 110) have the same structure 

 as those of higher organisms, 

 possessing a nucleolus and a 

 framework of delicate threads. 

 They increase in number by 

 division, as the plasmodium 

 grows. 



We see, then, that the 

 plasmodium of a Myxomycete 

 is a typical example of non- 

 cellular structure, consisting 

 of a perfectly continuous 

 protoplasmic body of large 

 size, containing vacuoles and 

 numerous nuclei, but entirely 

 destitute of any cell-wall. 



Sometimes the plasmodium 



passes into a resting condition, a change which often, 

 though not always, happens in consequence of drought. 

 The movements cease, and the protoplasm becomes 

 partitioned into a number of irregular cysts or cells, each 

 containing about ten or twenty of the nuclei. The cysts 

 are separated from each other by firm walls, which are 

 hardened portions of the protoplasm. In this resting 

 stage, which is known as the sclerotium, the plasmodium 



FIG. 1 1 0. Badhamia utricularis ; 

 portion of plasmodium, show- 

 ing a number of spherical 

 nuclei, in each of which the 

 fibrillar network and the 

 nucleolus is seen. Magnified 

 1200. (From Lister's Mono- 

 graph of the Mycetozoa.) 



