the Sieve- tubes in Laminarieae. 
1 1 1 
stage as that represented in Fig. 7, the layer of callus next to 
the sieve-plate, and which is coloured red in this figure, 
stained violet. I imagine this layer was not as yet completely 
converted into callus ; in other cases the inmost layer 
was coloured violet, and not the one next the sieve-plate. 
In all cases the sieve-plate itself turned blue. 
(6) Methylene bhte. — With this reagent negative results were 
found. The callus was not stained by it, nor by the majority 
of other aniline dyes. Eosin (in water) coloured the callus- 
plates a faint red, but only lasting so long as the preparations 
were kept in the stain. These negative results with Methylene- 
blue are highly characteristic of all callus. 
(7) Haematoxylin. — With dilute solutions the callus-plates 
stain deeply. 
(8) Hydrie sulphate . — As this is run in, the callus-plates 
gradually swell up, showing at the same time a very beautiful 
stratification. The swelling up goes on and the callus 
gradually becomes indistinct, and is finally dissolved. By 
dissolving away the callus in cases where the pores are not 
yet obliterated the connecting threads may be demonstrated 
by staining in Hoffmann’s blue, which shows them up in a 
very effective manner. 
(9) Potash. — Here also the callus swells up and becomes 
later indistinct ; I did not see however that it absolutely 
dissolved as in the case of the hydrie sulphate. 
It will be seen from this series of reactions in which the 
Laminaria-callus agrees with that found in phanerogamic 
sieve-tubes that the two substances are to be regarded as 
identical. This is the more remarkable from the fact that 
in hardly any other plants but Phanerogams is any callus 
found. 
In addition to the above enumerated reactions it should be 
mentioned that I find the Laminaria-callus to be isotropic. 
In this it further agrees with phanerogamic callus. 
The capacity for its development in these two sea-weeds is 
no doubt connected with the fact that both Macrocystis and 
Nereocystis attain to such a gigantic length without any 
