1912] GRIGGS—RHODOCHYTRIUM 139 
aside by gradual pressure (fig. 15). Generally the walls of these 
cells can be readily distinguished from that of the cyst, though they 
may be closely appressed to it. Such walls usually correspond 
approximately in length with the adjacent part of the parasite. 
This indicates, especially in those cells that have been much 
reduced in size, that they have shrunken considerably, for the 
original wall would have been much crumpled if merely pushed 
back by the expanding parasite. They often lose their sharp 
outlines and appear to be undergoing digestion. 
The supply of nutriment which makes possible the growth of 
the parasite is drawn from an extensive system of haustorial 
thizoids, which are put out from the basal portion of the young 
parasite even before the germ tube begins to swell out into the 
spherical cyst. They continue to increase and to extend their 
ramifications until the cyst reaches its full size and begins to ripen, 
finally extending considerable distances along the vascular bundles. 
But notwithstanding the wide extension of these elements and 
their filamentous form, they can hardly be compared with the 
hyphae of a true fungus. They are by no means to be looked upon 
~ as the vegetative portion of the plant from which the fruiting 
bodies take their origin, but merely as rhizoidal outgrowths from 
the main body of the parasite. When old they develop thick 
walls, especially in the portions close to the cyst. But at the 
extremities, where most of the absorption may be supposed to 
occur, the wall is exceedingly delicate or invisible. Although they 
sometimes work their way between the disorganizing cells, their 
course is for the most part within the cells which they invade 
(fig. 5), and their shape is often largely determined by the bounda- 
ries. of these cells. Both LAGERHEIM and ATKINSON speak only of 
those haustorial branches which become attached to the vessels of 
‘the system. But the great mass of the rhizoidal system is located 
in the phloem (figs. 4, 5, 15, 22), and it is the cells of the phloem 
which are most injured, finally breaking down completely, while 
the xylem is but little injured. It must also be obvious that the 
vessels could not furnish the supply of organic food necessary to 
nourish the parasite. There is no doubt, however, but that some 
of the ultimate branches of the haustoria do come into close relation 
