Structure and Affinities of Leuconostoc mesenteroides. 81 
product of hydrolysis of the constituents. According to 
Benecke(1) the chief substance is formed by the coming together 
of several molecules of glucose and the loss of water. In its 
solubility in strong acids and alkalis the membrane shows a 
difference in constitution from that of many algae. An investi- 
gation of the microchemical reactions of the membrane gave the 
following results. 
(a) Cellulose and schizophycose are absent. This is shown 
by tests with zinc chloriodide, iodosulphuric acid and the 
calcium chloride reagent of Mangin(9) and the insolubility in 
cuprammonia solution. 
(6) Proteins and amino-compounds are absent. Negative 
results were given by the xanthoproteic reaction, by Millon’s 
reagent and by haematoxylin, etc. (r). 
(c) Pectins are absent. Observations were made with ru- 
thenium red, safranin and methylene blue, all of which give 
characteristic reactions with pectic substances if neutral or 
slightly alkaline material be used(9). Control reactions with 
Nostoc and Microcystis, two algae having well-developed en- 
velopes superficially similar to those of Leuconostoc, stained red 
with ruthenium red and, with safranin and methylene blue, 
gave bright orange and violet coloration respectively. On the 
other hand the material of Leuconostoc did not fix ruthenium 
and gave rose-red and blue colorations with safranin and 
methylene blue respectively. 
(2d) The mucilage of Leuconostoc has several of the reactions 
of callose, viz. insolubility in cuprammonia solution, staining 
reaction with anilin blue, corallin soda, negative reaction with 
zinc chloriodide and iodine. Unlike callose it does not stain 
with haematoxylin, is insoluble in dilute alkalis and is optically 
active. 
The envelope is the most striking feature in the morphology 
of Leuconostoc mesenteroides. Structures of comparable form are 
met with in the Chroococcaceae and the Nostocaceae among the 
Cyanophyceae and in the Tetrasporales and Heterocapsales 
among the Isokontae and Heterokontae respectively. Many 
Cyanophyceae are partially saprophytic and that holosapro- 
phytic members of the group might exist has long been sus- 
pected. It is now recognised that palmelloid types have de- 
veloped independently along various lines of evolution. In 
Leuconostoc as in many other capsulated organisms, the envelope 
is not always present (f. muda) and we have already referred to 
the variability in external form of the colonies. The mere 
possession of the envelope is, therefore, by itself, no criterion of 
affinity. Moreover, those algal envelopes which approach most 
closely in external form to that of Leuconostoc differ from the 
M.S. 6 
