284 Prof. H. Karsten on the Formation, 



itory secretion-cells or the early stages of development of new 

 joint-cells. 



It has been satisfactorily shown by former observers, and 

 especially by Bary, that the thickened membranes of (Edogonium, 

 and particularly the extensile annular fold, behave with reagents 

 like cellulose. To these statements I can add that this annular 

 fold consists solely of cellulose, even before its extrusion. 



In the ordinary course of development of (Edogonium, this 

 investigation is difficult, on account of the instantaneous rupture 

 of the membranous envelope, and the sudden extension of the 

 fully developed fold, on the application of the reagents necessary 

 for these experiments. 



In specimens placed in the direct rays of the sun, in order to 

 excite them to more rapid development, but which had to sup- 

 port a temperature too high for their normal vegetative activity 

 (namely, 35° Reaumur), the membranes of the secondary cells 

 acquired considerable thickness whilst yet enclosed within the 

 primary cells, which still exhibit their annular folds, as shown in 

 fig. 25. 



In these cells it could be seen distinctly that the annular 

 constriction consists entirely of cellulose — that is to say, that it 

 exhibits the cellulose reaction with solution of iodine and chloride 

 of zinc — as the annular fold did not extend itself even on the 

 application of that reagent. 



The contents of these unusually thickened cells consisted of 

 comparatively large hyaline non-nucleated cells, with pale-green 

 starch- and chlorophyll-corpuscles and reddish- coloured oil- 

 drops (?) thinly scattered between them. A large accumulation 

 of chlorophyll was observed in the upper end of the cell. 



These (Edogonia soon became quite colourless; the large 

 transparent vesicles disappeared ; and only the oil-particles, and 

 especially the decolorized starch-corpuscles, remained undis- 

 solved and unchanged in the dead membranes for any con- 

 siderable time; even the annular fold vanished by solution, 

 though the rest of the same cell-wall continued unaltered. 



Similar individuals, with greatly thickened secondary cells, I 

 have observed now and then among normally developed forms. 

 In these also the annular fold had not expanded, though the 

 investing envelope, consisting of a double membrane (probably 

 the cuticle and the remainder of the membrane of a primitive 

 mother cell), was annularly torn through above it. Indeed, in 

 a few days, the fold was dissolved in the water, and its former 

 existence evidenced only by an empty space. In these cells two 

 young joint-cells had been formed — one, the larger, occupying 

 the space below the annular fold, the other the small space of 

 the mother cell above that fold. Both these young cells were 



