Igor | ANATOMY OF THE OSMUNDACEAE 391 
of the vascular cryptogams may not be identical with that found 
in phanerogams ; (2) it occurs in minute quantities only, and in 
some plants (e. g., the Ophioglossaceae) probably does not occur 
at all; (3) its presence is determined by delicate microchemical 
means, and then only by limited color reactions. 
Janczewski*'+ claimed to have found callus in Preris aquilina 
alone of all the vascular cryptogams he examined, and states 
that it does not occur in O. regalis. The reagents he used were 
Schulze’s solution (or chlor-zinc-iodin) and rosolic acid. On 
the other hand, Russow found callus in all of the sieve tubes he 
examined. The reagent he used was a mixture in variable pro- 
portions of chlor-zinc-iodin and potassium iodid-iodin. It 
should be stated that in the vascular cryptogams callus occurs in 
_ the wall of the sieve plate, appearing as if it were a part of the 
wall. After staining with a suitable iodin solution, the callus 
shows in- face view as one or more round brown spots, and in 
section as rods or granules occupying the entire thickness of the 
lamella. Poirault has largely corroborated Russow’s observa- 
tions. He disagreed with Russow’s generalization that it is a 
constant feature of sieve tubes, for he states that he has been 
unable to find any trace of callus in Angiopteris and Ophioglos- 
sum.'S In view of these investigations, therefore, it becomes a 
matter of interest to know if the sieve tubes of Osmundaceae 
Show the phenomena of callus as described by Janczewski for 
Pteris, and by Russow and Poirault for many others of the vas- 
cular cryptogams. 
Accordingly tangential and transverse sections about five 
microns thick, of the three Osmundas studied and of 7. barbara 
were cut from mature pieces of stem embedded in celloidin. In 
the present research the writer has tried several stains, such as 
Tuthenium oxid, Hofmann’s blue, rosolic acid, and Russow’s 
mixture. These have been applied to sieve tubes of plants from 
widely separated groups, such as Vitis (summer and winter sieve 
tubes), Tilia, Pinus, Pteris, and the mixture of chlor-zinc-iodin 
“ JANCZEWSKI: Tubes cribreux. Ann. Sci. Nat. Bot. VI. 14:50. 1882. 
*S POIRAULT : of. cit. 192. 
