Schwartz.—■Parasitic Root Diseases of the Juncaceae . 515 
a root-hair, not necessarily at its extremity, and by the repeated division of 
this nucleus a chain of nuclei is produced, with the result that the root-hair 
is completely filled with the protoplasm and nuclei of the amoeba, and thus 
the organism reaches the base of the hair and the outer cortical cells of the 
root. These root-hairs are long and sufficiently strong to resist being torn 
in the process of removing the plant from the soil. In some roots a con¬ 
siderable number of the hairs exhibit the presence of these amoebae. 
It is thus evident that, whereas in the case of Veronica plants the 
infection is a primary one, taking place at the growing apex, in the case of 
J uncus roots it may occur through many root-hairs and at various times 
during the growth of the root. That the outer cortical cells of the root may 
be directly infected without the intervention of a root-hair, is no doubt 
possible, though I have not actually observed it; further, it is probable that 
the superficial layers at the growing apex may be infected, and so give rise 
to diseased outer cortical cells; this is rendered likely from the fact that 
diseased cells are sometimes found in longitudinal rows. 
The nuclei of the amoebae divide by a process to be described later, 
without any division of the amoebae themselves. In this way the amoebae 
increase in size until they completely fill the root-cells that contain them; 
at the same time, the granular protoplasm of the organism is clearly 
differentiated from that of the plant-cell, from which also it may be dis¬ 
tinguished by the presence of oil-drops. At times these plurinucleate 
amoebae behave as schizonts, inasmuch as portions are split off, thus giving 
birth to uninucleate or multinucleate daughter-amoebae — the so-called 
‘ meronts The shape of the amoebae may be rectangular, which is the 
case when they occupy the whole of the root-cell, or it may be ellipsoidal, 
or roughly spherical; it is in these latter cases that the splitting off of 
meronts, or schizogony, as it is called, is usually to be observed. There is 
no formation of a plasmodium by the coalescence of different amoebae; 
indeed, a root-cell containing more than a single amoeba is rarely found. 
Nuclear division during the vegetative phase. As in the cases of 
Plasmodiophora Brassicae and Sorosphaera Veronicae , we meet with the 
same process of nuclear division in 6’. Junci. It is only after the examina¬ 
tion of a very large number of nuclei that any of the stages of nuclear 
division can be discovered. This is probably due to the short time required 
by the nucleus for the act of division, and also to the difficulty of rapidly 
fixing a root which has been taken from a muddy soil. In any amoeba the 
nuclei seem to divide simultaneously, so that all its nuclei may be seen in 
the same phase of the division. The first change to be observed in the 
nucleus prior to division is that it becomes somewhat elliptical in shape, 
then the karyosome elongates, and at the same time the chromatin granules 
collect into an equatorial plate, and we have the cruciform figure described 
by various observers in P . Brassicae and .S'. Veronicae. Viewed from the 
