Magnus,— On A ecidium graveolens (Skuttleiv.). 157 
difference in the relation of these mycelia to the tissues of the 
host-plant has ever been observed. Therefore I cannot accept 
Eriksson’s hypothesis that the mycelium of the aecidiospores 
can bear any relation to the tissues of the branches of the 
witches’ broom, differing from that of the mycelium developed 
out of the germinating sporidia of the teleutospores. 
The investigation of the fresh material, as I have already 
mentioned, has confirmed my earlier observations. The 
hyphae are always intercellular, and put out knot-shaped 
haustoria into the cells between which they grow. They 
occur in the pith, in the cortical parenchyma, in the phloem, 
and in the medullary rays (I had forgotten to mention the 
last in my communication of February, 1897). In the me- 
dullary rays the walls of the cells on which the hyphae grow 
are swollen (Figs. 7-9), and the hyphae send out numerous 
knot-like haustoria into the parenchymatous cells. I could 
not be certain that haustoria are also sent out into the wood- 
cells bordering on the medullary rays. I believe that this 
does take place, but I am not satisfied that the cells in which 
it seems to occur are not medullary ray-cells. In the elon- 
gated cells of the phloem the branches of the haustoria are 
sometimes not coiled up into a knot, but lie free in the cell 
(Fig. 6). The branches are not straight, but are curved or 
crumpled, and constricted here and there. As I have de- 
scribed earlier (loc. cit.), the mycelium is formed in the young 
branches of the witches’ broom in the pith, in the medullary 
rays, and in the primary cortical parenchyma. In the latter 
it is often cut off from the surrounding tissue by the formation 
of cork in the infected tissue, so as to form island-like masses 
in the cortex h 
Out of the primary cortical parenchyma in the older twigs 
the mycelium grows into the phloem and gradually penetrates 
into it as development proceeds. In the phloem also the 
infected parts of the tissue are often enclosed as islands by 
the formation of cork. These ring-like formations of cork 
Vide Berichte der Deut. Bot. Ges., Bd. xv, 1827, Taf. iv, Fig. 5. 
