Magnus. — On A ecidium graveolens (Shull lew.). 159 
and especially into the spaces between the vascular bundles 
where the leaves come off. These mycelial strands grow next 
spring into the buds which are formed at this place, and form 
spermogonia and aecidia over the whole surface of their 
leaves. 
I will here shortly recapitulate these observations. The 
mycelium always grows between the cells, and gives off 
haustoria into them. In the first spring the hibernating 
mycelium grows into the developing buds, and forms sper- 
mogonia and aecidia on the whole surface of the first leaves. 
In the case of those short shoots which grow out into branches 
with long internodes, the mycelium grows directly into the 
pith and continues to grow with the merismatic tissue. This 
also takes place in the spring. From these medullary 
mycelial strands branches grow outwards, but these do not 
penetrate into the leaves. They pass through the medullary 
rays into the primary cortical parenchyma, and especially 
through the openings in the vascular cylinder, where the 
young leaves are given off to the axillary buds, from whence, 
in the following spring, the mycelium enters into the first 
developing leaves. As the branches of the witches’ broom 
increase in thickness, the mycelium spreads from the primary 
cortical parenchyma into the phloem. Both in the primary 
cortical parenchyma and in the phloem the rows of cells 
affected by the mycelium are enclosed more or less com- 
pletely by a cylindrical cork-formation, and are thus separated 
from the less affected tissue. 
What, then, is the tubular mycelium in the cambium-cells 
described and figured by Eriksson (loc. cit Fig. 5, PI. II), 
containing, contrary to what is observed in the mycelial 
strands of Uredineae growing in tissues not exposed to light, 
the yellow colouring-matter of the Uredineae? Leaving aside 
for the present the yellow colouring-matter, his figure re- 
sembles more than anything else the young cells of the 
cambium with horizontal transverse walls, the contents of 
which are contracted by plasmolysis. It is often the case 
in elongated cells that the plasmolyzed contents are for the 
