UREDOSPORES 9 
THE UREDOSPORES. 
The germ-tube soon forms a more or less extensive my- 
celium, which may penetrate the greater part of the leaf’ of 
the Carex, but in many species of Puccinia is strictly localised 
to a small defined spot. All its cells are binucleate, like the 
spore from which it originated. The cells of the mycelium, in 
every stage, send haustoria into the cells of the host; when an 
haustorium arises from a binucleate mycelium, it is itself 
Fig. 8. Section of leaf of Carex paludosa, with a sorus of uredospores of 
P. Caricis; a, upper epidermis; b, a vascular bundle. Most of the 
pedicels have lost their spores. x 180. 
likewise binucleate. After a few days this mycelium begins to 
form the third kind of spore—the uredospore. A knot of 
hyphz is formed just beneath the epidermis; some of the 
branches turn upwards and form a regular 
layer parallel to the surface—the spore- 
bed (Fig. 8). 
The upper rounded cell of each hypha 
is divided into two daughter-cel]s, the 
lower of which is developed into a 
stalk, the upper becomes the uredospore 
(Fig. 9). The spore is oval or roundish ; 
when mature it is enclosed in a double 
cell-wall, the outside being cutinised and wig.9. P. Caricis. De- 
provided with spine-like projections, some- veloping uredospores 
2 cones (1, 2, 3, 4, show stages 
what like those of the scidiospore, only of growth ; 5 is a pe- 
more pointed. In the inner layers of the _ dicel from which the 
spore has vanished). 
exospore there are usually three (rarely z 500. } 
