732 MINNESOTA BOTANICAL STUDIES. 
comparable with A/arza. The structure of the stipe differs 
decidedly from that of ZLessonza which I have previously ex- 
amined.* In both genera there are strongly marked growth- 
rings which, as will be seen, do not arise in precisely the same 
way. A detailed account of the anatomy follows. From it 
some notion may be derived of the histological interrelation of 
Pterygophora, Laminaria and Lessonia. 
The most important literature on the anatomy of the Lamina- 
riacee has been previously cited ¢ and it will not be necessary ~ 
to refer to it further at this time except as some particular point 
may require elucidation. To the papers of Wille, Grabendorfer, 
Reinke, Rosenthal, Oliver, Ruprecht and-others students are 
indebted for researches which have laid the foundation for a 
knowledge of the anatomy of the Laminariacee. 
The holdfast.—The study of this structure as of the other or- 
gans of Pterygophora is based upon a series of slides prepared 
from material collected at the Minnesota Seaside Station,’ 
killed in chromic acid, and transferred into 70 per cent. alcohol 
in which condition it was brought to Minneapolis for study. 
Most of the sections have been cut freehand, treated with various 
reagents and stains and mounted in glycerine-jelly. _Russow’s 
callus reagent, chlor-zinc iodide and a variety of stains, includ- 
ing particularly the fuchsin and iodine-green combination and 
aniline water safranin, have been employed to bring out de- 
tails of structure. 
The primitive disc shows no points of special interest, not 
differing particularly in structure from that already described 
for Vereocystis,t nor at first do the hapteric branches in their 
origin and structure show characters worthy of especial com- 
ment. The haptere originates through the activity of a circu- 
lar cambial area at the edge of the primitive disc or from the 
lower rhizogenous area of the stipe. Callosities on the stipe, 
such as those described for Vercocyst7s and there believed to be 
equivalent to hapteric branches, have not been discovered in 
Pterygophora, though on one specimen some curious gall-like 
swellings, doubtless teratological or pathological in their nature, 
were observed. The numerous hapteric outgrowths of Ptery- 
*MacMillan, C. Observations on Lessonia, Bot. Gaz. 30: 318. pl. 19-27. 
1900. 
ft MacMillan, C. Llc. 
t{ MacMillan, C. Observations on Nereocystis, Bull. Torr. Club, 26: 273. 
pl. 367, 362. 1899. 
