PUCCINIA POARUM 47 
as shown in radial section. The outer edge of each cell is more 
prolonged downwards so as to overlap a portion of the cell 
below in an imbricated manner. The xcidium, in both, as is the 
{ 
Fig. 27. P. Poarum. An excidio- 
spore germinating on leaf of 
Poa annua. x 180. 
Fig. 26. P. Poarum. Vertical section 
through edge of excidium; showing a, 
the crushed cells of the upper myce- 
lium, pushed on one side ; b, the chain 
of peridium-cells; c, the spore bed, 
giving rise to d, the chains of scidio- 
spores. x 600. The black dots are 
the nucleoli; one #cidiospore-mother- 
cell has three nuclei. 
case in most of the higher forms 
of the Uredinales, arises deep Fig. 28. P. Poarwm. u, an weidio- 
- spore germinating in water, 
in the leaf, and the densely x 250; b, the same, showing 
packed knot of hyphe which — he germ-pores, x 500. 
forms the starting-point of the hymenium, where the cells are 
full of protoplasm, is covered over by a number of nearly empty 
cells which are ultimately squeezed to the side by the develop- 
ing eecidium and are shown in the figure at a. 
It is easy to produce the teleutospores in a garden on a tuft 
of (say) Poa annua or P. pratensis, by planting quite near to it 
