Structure and Affinities of Leuconostoc mesenteroides. 77 
From the above-mentioned investigations, the main features 
of the organisation of Leuconostoc mesenteroides are well known, 
but in the present account attention may be drawn more par- 
ticularly to certain characters which have a bearing upon the 
affinities of the plant and which previously have been over- 
looked. Only the typical species Leuconostoc mesenteroides 
(Cienk.) van Tieghem was studied. No doubt a number of allied 
species exist (6). 
When grown in liquid media containing sucrose the colonies 
assume the form of rounded, slightly elongated, translucent, 
white masses, very variable in size but often over I cm. in 
length and 1-5 to 2c.c. in volume. It is stated that under 
special conditions the individual masses may attain a much 
greater size than this, and may even occupy volumes of several 
hundred c.c. The colonies normally show a characteristic deeply 
folded or cerebriform surface which gives the plant its specific 
name. In cultures on some solid media (e.g. beet) they retain 
this character, but on.others (e.g. various agars) this is less 
obvious and may be absent, the colonies tending toan amorphous 
form, especially on media which restrict the production of 
mucilage. The colonies of the sheathless form obtained by 
Liesenberg and Zopf are of course amorphous. Macroscopically 
the normal colonies can be distinguished clearly from those of 
certain rod-bacteria of similar mode of life and which form the 
so-called rice-grain of sugar-works. 
The growth of these colonies is often extremely rapid. Under 
favourable circumstances a volume of forty-nine hectolitres of 
Io % sugar solution was filled in the course of twenty-four hours 
with these spawn-like masses(4). Of course the great bulk of 
the organism depends on the mucilage and actual average 
measurements show this, in 10 % sugar solution, to occupy at 
least one hundred times the volumes of the protoplasts them- 
selves. The same result is obtained if we compare the rate of 
growth of the colonies on media containing glucose with that 
on sugar-free media. 
Reproduction of the colonies of Leuconostoc takes place very 
largely by vegetative breaking. The development of the colony 
from a single cell has been described by van Tieghem and by 
Liesenberg and Zopf. According to these authors the cell sur- 
rounds itself by a mucilage capsule and divides to form a 
filament. The capsule eventually gives place to a tubercular 
mass of numerous capsules so that a section of the thallus has 
a pseudoparenchymatous appearance. I find that this is well 
seen in preparations made with ordinary bacterial capsule 
stains (Friedlander, Welch). According to van Tieghem this 
segmentation of the capsules is due to the constriction of the 
