731 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 Fucaceas. It has been described by Reinke* 

 as a fatty oil, in which view Hansen f practically coincides and 

 considers that the Phaeophycea? in general produce fat instead 

 of starch by their assimilation. The same material, however, 

 has been described as Phaeophyceenstarke 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 

 Pterygophora 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- 

 nariaceae, it may be said that the ringed appearance of hapteric 

 branches in 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. fur wis- 

 sensch. Bot. 10 : 317. 1876. 



t Hansen. Ueber Stoffbildung bei den Meeresalgen. Milth. Zool. Stat. 

 Neap. IT : 276. 



