16 HOEMEISTER, ON 



by means of six triangular septa, passing between each two 

 nuclei, and cutting each other in the middle point of the 

 cell. The wall of the mother-cell increases manifestly in 

 thickness from the time of the appearance of the secondary 

 nuclei until the formation of the septa. In Anthoceros lavis, 

 it remains smooth ; in Anthoceros punctatus it is furnished 

 with numerous dots {Tilpfeln) ; (PL III, fig. 23). The 

 inner layers of the thickened wall are very sensitive to the 

 action of water, especially in Anthoceros l 'avis ; they swell 

 up rapidly, and to a great extent, contracting the cavity of 

 the cell, and compressing its contents into a small space, 

 causing great difficulties to the observer. The affinity of 

 the swelling layers for water is so remarkable, that the 

 swelling takes place even in saturated saline solutions. 

 Alcohol is the only medium in which it fails to occur ; it 

 is very much diminished in diluted alcohol. If spore- 

 mother-cells, in which the four tertiary nuclei are fully 

 formed, are placed in diluted alcohol, the cell-contents first 

 contract ; a slight swelling of the membrane of the cell 

 then begins, which increases in proportion as the alcohol 

 escapes by evaporation from the fluid. It is now plainly 

 seen that it is one of the middle layers in particular of the 

 cell-wall which increases in size by absorption of water 

 (PI. Ill, fig. 11). The outermost layer of the membrane 

 passively follows the increase in size of the middle one, and 

 becomes expanded. If pure alcohol is added, water is 

 withdrawn from the swollen membranous layer ; the latter 

 diminishes in size ; the outer layer of the cell-wall there- 

 upon becomes wrinkled, inasmuch as its volume does not 

 diminish in the same proportion as that of the middle 

 layer, and its elasticity does not equal its power of ex- 

 pansion. H. v. Mohl has shown that the formation of 

 the septa of the mother-cells progresses gradually from the 

 periphery to the centre ; and he has figured a condition in 

 which this growth has taken place to so small an extent 

 that the yet imperfect septa have not interfered with the 

 strings of protoplasm uniting the four tertiary nuclei.* The 

 rapid swelling up of the walls of the mother-cells prevented 

 me for a long time from repeating this observation, which 



* 'Linnee-a,' 1836; " Vermischte Schriften," tab. iv, fig. 23. 



