Bailey , — Puccinia malvacearum and the Mycoplas?n Theory. 179 
detached leaves, but in this case one leaf was entirely submerged, whilst 
another similar leaf frorruthe same plant was kept in moist air. The results 
of these three series were uniform in one respect: in every case the pustules 
which were exposed to the air germinated to form promy celia and sporidia 
in the normal manner. The behaviour of the submerged leaves or portions 
of leaves was not so regular ; sometimes oidia only were produced, some- 
I 
Fig. 1. Teleutospores of Puccinia malvacearum germinated in sterile tap-water in a watch-glass, 
I. Shows typical sporidial germination of a spore lying on surface of water. 
II. ‘ Oidial ’ germination of a spore at bottom of watch-glass. 
III. Shows ‘oidial’ germination (a) from the proximal cell (whole of germ tube under surface 
of water) and sporidial germination (b) from distal cell (the three last segments of the germ tube 
are above the surface of the water). 
(Magnification, 380 diameters.) 
times a mixture of oidia and abortive germ tubes, more or less intermediate 
between the two types, and sometimes, but much more rarely, a normal 
crop of sporidia was formed. 
These apparent irregularities are without doubt due to one of two 
causes : either the whole surface of the leaf was not in every case thoroughly 
wetted, or the pustules had already started to germinate before they were 
submerged. That this is the correct interpretation cannot be doubted when 
