448 SECOND PART.—MFCETOZOA. 
two genera, as far as isat 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" 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 momentithat 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 ata 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. III, Nr. 22. 
