i. 
which is closely appressed to the epidermis of the dead Dahlia 
stem. 
Under the low magnification of an ordinary Leitz dissecting 
microscope these tree-like condia-bearers are very distinctly dif- 
ferentiated. The central stouter filament may be detected run- 
ning from the mycelial cushion to the very end of the conidia- 
bearer. Along the upper two-thirds it is covered with the close 
whorls of conidial-branches, arranged for the most part in fours, 
and becoming briefer and less complicated towards the summit, 
until, near the apex, they becon:# reduced to slight protuberances 
barely prominent on the sides of the erect, stout, central filament. 
The very apex of this central filament is prolonged into a cylindro- 
conical hypha, so that the whole shape of each conidia-bearer 
may be roughly compared to the contour of a half-grown tree of 
Pinus Strobus, L., or perhaps even better, to some of the slenderer 
species of Avaucaria with their distinctly whorled branches. Ex- 
amination of a considerable number of plants was made, under 
powers of from four hundred and fifty to nine hundred diameters, 
and several different stages in the maturation of the conidia- 
bearers were noted in detail. An effort was made to trace the 
complete development of these organs. 
The first appearance of the conidia-bearer is as an erect, 
densely protoplasmic protuberance from a thread of the mycelial 
cushion. This protuberance increases rapidly in length, retain- 
ing throughout its growth a strong zenotropic (apogeotropic) 
irritability, and a horizontal septum is developed, cutting off a 
distal, from the basal cell. The distal cell, together with the 
basal cell, undergoes further elongation, and in the considerably 
denser contents of the distal cell numerous vacuoles make their 
appearance, but, in so far as seen, do not attain to any very great 
size, remaining, on the contrary, about one-quarter the diameter 
of the cell in which they appear. Synchronously there appear 
protuberances, at first scarcely perceptible, then rapidly elongat- 
ing into thread-like projections, upon the wall-area of the distal 
cell. Originally these protuberances are isodiametrical, but be- 
fore they equal in length the diameter of the cell producing them 
a swelling in the free end of the projection is seen to take place. 
The growth of the branch now continues in such a way that the 
