734 MINNESOTA BOTANICAL STUDIES. 
which the contents are less dense, will appear, and this alter- 
nation continues even into the cambial zone where single layers 
of cells will be found with the denser contents alternating with 
layers showing the opposite appearance. Besides this differ- 
ence others have not been discovered to account for the ringed 
appearance of old hapteres. 
As to the substance in the cells which by its greater density 
gives the ringed appearance it does not seem to differ from the 
material which has been studied by a number of observers, 
especially in the Fucacez. It has been described by Reinke * 
as a fatty oil, in which view Hansen f practically coincides and 
considers that the Pheophycee in general produce fat instead 
of starch by their assimilation. The same material, however, 
has been described as Phzeophyceenstarke by Schimper, as 
fucosan by Schmitz and Hansteen, as showing a tannin reac- 
tion by Berthold, as phloroglucin-containing material by Bruns, 
as connected with physodes by Crato and as polysaccharids, in 
constitution allied to mucine, by Koch. In the holdfast of 
FPterygophora the material sometimes fills the whole cell with a 
homogeneous refringent mass, which in the denser parts of the 
ring has decidedly the same appearance optically that is shown 
by the polysaccharid granules of the lamina and stipe to be de- 
scribed later. In other instances the refringent bodies may be 
distinguished from a generally granular protoplasmic slime 
which encloses them. Without going into the disputed ques- 
tion of the true chemical character of the cell-contents of Lami- 
nariacez, it may be said that the ringed appearance of hapteric 
branchesin Pterygophora is due to the alternately more vigorous 
and less vigorous production of certain substances connected 
with the assimilative processes of the plant. These substances 
occur in the stipe and lamina as well as in the hapteres, but are 
there not invariably the cause of a ringed appearance, being 
disposed in special cells without any apparent reference to the 
rhythm of secondary growth. 
The stipe.—Sections were taken first from plant ‘‘ B,” the uni- 
laminate stage and then from mature plants. In none of them 
could the mucilage ducts of Ruprecht be discovered and 
* Reinke, J. Beitraege zur Kenntniss der Tange. Pringsh. Jahrb. fiir wis- 
seusch. Bot. 10: 317. 1876. 
{ Hansen. Ueber Stoffbildung bei den Mecresalge: ‘fitth. Zool. Stat. 
Neap. Il: 276. : 
