141 
already recommended by Russow and Janczewskl for tlie study of 
liber, the color reagents of callose are certain substances of the series 
of azo colors, belonging to the group of benzidines, tolidenes, etc. 
Iodated reagents give to callose a yellow tint. Callose is therefore as 
distinct as cellulose or the pectin compounds. It is not a result of the 
artificial decomposition of the latter substances, for these may be treated 
in all sorts of ways without producing the reactions of callose. Its in¬ 
solubility in the cnprammoniacal reagent, even after the action of 
acids, and the yellow color which it gives with iodated phosphoric acid 
distinguish it from cellulose, while its insolubility in cold ammonia and 
alkaline carbonates, and its inertia toward stains which act on the pec¬ 
tin compounds separate it not less clearly from the latter. 
While callose exists normally in certain regions of the reproductive 
organs of phanerogams (pollen grains, pollen tubes, etc.) and vascular 
cryptograms, it is not found in the vegetative portions of these plants, 
exclusive of the liber, save accidentally and as irregular masses scat¬ 
tered through the cells. But in the thallophytes callose acquires a 
great importance. In the fungi it forms the membrane of the mycelium 
and of the organs of fructification in the most widely separated fami¬ 
lies ; e. g ., Peronospome, Saprolegniaceae, Basidiomycetes, Ascomycetes, 
Saccharomycetes. In lichens callose exists in the mycelial filaments, 
but not in the gonidia. It does occur, however, in some of the algae. 
On the other hand, he has not yet found it in certain Uredineae, nor in 
the mycelium and conidiopliores of the Mucorinae. In the plants of this 
order Mucor, Phycomycetes, Rliizopus, Pilobolus, Cliaetocladium, etc., 
it constitutes only the dissolving wall of the sporangium, and some 
part of the membrane of the spores. Callose appears to be in a state 
of purity in the membrane of the sporangium of the Mucorinae, but in 
the mycelium of the Peronosporime and Saprolegninae it is intimately 
united with cellulose, to the exclusion of pectin compounds, and, finally, 
in the Polyporei (Daedalea), the mycelial tubes appear to be destitute 
of cellulose, and are formed of callose associated with substances having 
the reaction of pectin compounds. 
Various circumstances often mask the presence of callose, such as 
physical differences or the incrustation of foreign substances, for exam¬ 
ple, the callose of pollen mother cells and that which forms irregular 
masses in the mycelium and haustoria of the Peronosporinae presents 
the most alterable and easily distinguishable state. In the sporangium 
of the Mucorinae and the mycelium of lichens the callose offers more 
resistance to the action of solvents and fixes stains less readily. Finally, 
in the Polyporei it coheres so strongly that its presence can be demon¬ 
strated only after long and repeated treatments. 
(2) The various stains of the aromatic series may be divided into 
two groups, one consisting of basic colors united with various mineral 
or organic acids, the other of acid colors used in the form of alkaline 
salts. Substances of the first category are fixed with a variable energy 
16788—No. 2-6 
