448 SECOND PART. MYCETOZOA. 



two genera, as far as is at present known, do not form plasmodia, but each swarm-cell 

 after absorbing food becomes the mother-cell of a new generation of swarm-cells. 



Plasmodiophora Brassicae is parasitic on the roots of cruciferous plants, 

 especially species of cabbage, and causes large swellings on them. An amoeboid 

 swarm-cell with cilia escapes from the round thin-walled spore in water, and pene- 

 trates without first undergoing division into the epidermis of the young root and from 

 thence into the parenchymatous tissue. Then the cells of the host become greatly 

 enlarged and large bodies with amoeboid movements make their appearance in them ; 

 but it could not be certainly determined whether these bodies were due to the growth 

 of one swarm-cell, or to the coalescence of several swarm-cells as in the Myxomycetes, 

 or possibly to a modification of the protoplasm similar to that which occurs in 

 Rozella (see page 395). Ultimately the entire protoplasm contained in a cell of the 

 parenchyma becomes motionless and divides simultaneously into a very large number 

 of spores of the character stated above, and in this case also without previously 

 forming a special membrane. 



Finally Zopf 1 appears to include all sorts of lower organisms with amoeboid 

 movements together with some of the forms last described under the name of ' lower 

 slime-Fungi.' This use of the term does certainly not correspond with the meaning 

 hitherto assigned to it, and to avoid any misunderstanding I say very distinctly 

 that this application of the term and therefore also the discussion of any other forms 

 than those which have now been mentioned cannot be admitted in this place. 



CHAPTER IX. MODE OF LIFE OF THE MYCETOZOA. 



SECTION CXXVI. Germination. The spores of the Mycetozoa, in which 

 the germination has been observed, are able to germinate from the moment that they 

 are ripe. Some retain the power of germination for a long time if protected from 

 injury ; many Calcareae, for example, Physarum, Didymium, Chondrioderma, Peri- 

 chaena liceoides, retain their vitality 2-3 years, some, as Physarum macrocarpum 

 according to Hoffmann, eve for 4 years. In Trichia varia and T. rubiformis 

 vitality lasted according to express observations only 7 months ; in other species of 

 Trichia and allied forms it appears to be extinguished at a still earlier period. 



The requisite conditions for germination in most known forms are the usual 

 spring and summer temperature of our temperate climates and a sufficient supply of 

 water. The majority germinate readily when placed in pure water, well developed 

 fresh material often in a few hours. Nutrient substances dissolved in the water do 

 not hinder germination; this at least was found to be the case in Fuligo and 

 Chondrioderma. The Ceratieae and such Acrasieae as have been examined do not 

 germinate in pure water, but only in a suitable nutrient solution. The like necessity 

 and the use of unsuitable solutions may account for the want of success which has 

 attended the attempts hitherto made to procure the germination of their spores of the 

 Cribrarieae and Tubulina. 



1 See Biolog. Centralblatt, Bd. Ill, Nr. 22. 



