732 MINNESOTA BOTANICAL STUDIES. 



comparable with Alaria. The structure of the stipe differs 

 decidedly from that of Lessonia 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 

 Ptcrygophora, Laminar ia and Lessonia. 



The most important literature on the anatomy of the Lamina- 

 riaceae has been previously cited f 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 Laminariaceae. 



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 Ncreocystis,\ 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 Nercocystis and there believed to be 

 equivalent to hapteric branches, have not been discovered in 

 Ptcrygopkora, though on one specimen some curious gall-like 

 swellings, doubtless teratological or pathological in their nature, 

 were observed. The numerous hapteric outgrowths of Ptcry- 



* MacMillan, C. Observations on Lessonia, Bot. Gaz. 30: 318. pi. 19-21. 

 1900. 



t MacMillan, C. 1. c. 



% MacMillan, C. Observations on Nereocystis, Bull. Torr. Club, 26: 273. 

 pi. j6f, 362. 1899. 



