STUDIES ON CLUBROOT OF CRUCIFEROUS PLANTS 



435 



former method of locomotion in the living cells, and mentions it as the 

 means by which the organism moves. Schwartz (1910), on the other 

 hand, observed the growing of the amoeboid tip in Ligniera Jumi (Sch.) 

 M. et T., and explains the change of position on that basis alone. A root 

 hair is shown in figure 104, D, which apparently was infected near the tip, 

 and as the organism grew rootward fission took place, so that when the 

 anterior part of the amoeba eventually reached the base of the cell the 

 root hair was filled completely with the meronts, as Maire and Tison 

 (1911) designate the segmented parts (fig. 103). This does not always take 

 place, for there were many more cases observed in which the intact 

 amoeba reached the base of the cell (fig. 104, E, F). In either case, if the 

 time consumed is too long, or if 

 for any other reason sporulation 

 begins, the amoeba loses its 

 power of further penetration 

 into the cortical tissues. If, 

 however, it reaches the inner 

 wall of the root-hair cell, its 

 pseudopodia are extended into 

 the very smallest thread-like 

 processes, which pass thru and 

 into the cortical cell (fig. 105, 

 E, F,G). Schwartz (1910), in de- 

 scribing penetration by Ligniera 

 Junci, gives the same route of 

 invasion but does not state how 

 the passage from the epidermis 

 into the cortical cells takes F '" l - 3 ' PHOTOMICROGRAPH^ CELLS CONTAIN- 



place. ThlS question IS OI eS- One amoeba has elongated considerably and is separating 



pecial interest, since in the 



latter part of his discussion Schwartz states his belief that amoebae never 

 have the power of penetrating cell walls. There is no other apparent 

 means by which this could be accomplished, for the epidermal cells seldom 

 divide periclinally. 



It would be difficult to explain the wide distribution of the parasite 

 within the root if cell-wall penetration did not occur, even tho it were 

 taken for granted that invasion begins in the apical cells. The rootcap 

 s ) fully protects these rapidly dividing primary cells that one must pre- 

 suppose that in order to reach them the organism can pierce the walls. 

 Then, in the maturer roots constant secondary thickening by the cam- 

 bium takes place, which would ultimately push most of the diseased cells 

 toward the periphery or isolate them near the center. This, however, does 



