193 Prof. H. Karsten on the Formation, 



The study of the history of development of the porous cells 

 in the pith of Huya carnosa, in the tissue of the stem of Langs- 

 dorffia, as also that of the porous and scalariform ligneous cells 

 of ferns &c,, led me to the knowledge of these conditions of 

 structure*. 



At the time it escaped my notice that Ungerf, in his instruc- 

 tive examination of the development of the spiral vessels in the 

 root-ends of Monocotyledons, had already arrived at similar 

 results, linger observed that the youngest vessels arising from 

 the coalescence of series of cells contained a mucilaginous fluid, 

 within which numerous small vesicles soon presented themselves 

 and became adherent to the walls of the vessels, which at a later 

 period underwent thickening, in part in a spiral manner, in the 

 intervals between these vesicles. 



A picture of the spiral thickening of secondary cells is fur- 

 nished by certain diseased states oi Spiroyyra mVen*, which have 

 been frequently referred to. When this plant has lain for some 

 time in carbonic-acid water, and is afterwards transferred to 

 pure water or to a very weak endosmotic solution, the chloro- 

 phyll-layers are observed to become, in consequence of diosmosis, 

 separated from the swollen secondary walls, as seen in PI. VII. 

 figs. 65, 66. In these now muco-gelatinous membranes they 

 leave behind them channel-like depressions, the membrane at the 

 parts between them being more strongly thickened, probably 

 from the absence here of impediments to diffusion. The pheno- 

 menon is very transitory, as the membrane continues to undergo 

 change by swelling up, and apparently becoming liquefied in 

 the water. 



Another picture, likewise, of a spiral arrangement is at times 

 seen in the progress of the changes of the cell-contents of 

 Mougeotia when placed in solution of tannin (vol. xiii. p. 418). 

 In this instance the secretion-cells do not adhere to the wall, but 

 occupy the entire cavity of the cell. 



Both these examples are probably types of spiral formation 

 as it actually proceeds in nature, though observable with very 

 great difficulty. In every case this formation takes place by 

 means of a thickening of the cell-membrane in the intervals 

 between adherent endogenous vesicles, just as the often observed 

 ridge-like prominences on the secondary pollen mother cells 

 (vol. xiii. p. 483) originate between the pollen-cells, the proper 



* De Cella vitali, p. 33, tab. 1. figs, a-d; Vegetationsorgane der Palmen, 

 tab. 8. fig. 1 J; Bau der Cecropia, Nova Acta, vol. xxiv. torn. i. p. 88, 

 tab. 13. fig. 4; Langsdorfiia, Nova Acta, vol. xxvi. torn. ii. tab. 63. 

 fig. 5. 



t Lmnaea, 1841, p. 385, taf. 6. See also Grundz. d. Anat. u. Phys. 

 1846, pp. 11 & 46. 



