292 HOPMEISTER, ON 



mucilage. This latter cell usually constitutes the first 

 radicular hair of the growing prothaUium (PL XXXVII, 

 rigs. 14—16). 



In Equisetum Umosum aii&palustre the upper chlorophyll- 

 bearing cell divides immediately by a vertical or strongly 

 inclined septum (PL XXXVIII, figs. 15, 16). In Equi- 

 setum arvense the cell often expands to a very considerable 

 extent before it divides, especially when the spore is sown 

 in a very moist shady place (PL XXXVIII, fig. 19). The 

 formative matter — protoplasm mixed with numerous chlo- 

 rophyll-granules — is accumulated at the apex of the upper 

 cell, which is turned away from the rooting end of the 

 growing prothallium. This mucilaginous mass usually, but 

 not always, surrounds the nucleus. The latter dissolves 

 gradually and two new ones take its place (PL XXXVIII, 

 fig. 19). A transverse septum, which makes its appearance 

 between the two, divides the large chlorophyll- bearing cell 

 into an upper, smaller cell, destined for further active division, 

 and a lower, distended, permanent cell (Pl.XXXVII, fig. 20). 

 The basal cell often grows into a tubular root after the 

 previous growth of one or more capillary roots from the 

 free outer wall of the younger cells. Frequently, however, 

 this does not take place (PL XXXVII, fig. 20). ' 



The further development of the prothallium is very 

 various. There is hardly any organ of the higher plants 

 in which there is so little regularity of cell-multiplication. 

 Usually there is a tendency to longitudinal growth by the 

 repeated division of one or more apical cells by means of 

 transverse septa, and also to the division of the cells of the 

 second degree by longitudinal septa. Lateral shoots are 

 very often formed. They are produced by the protrusion 

 of the wall of a somewhat older cell, and the subsequent 

 separation of the protuberance from the primary cell-cavity 

 by means of a transverse septum (PL XXXVII, fig. 20). 

 These adventitious shoots exhibit the like forms of cell- 

 multiplication as the primary shoots, which they often sur- 

 pass in vigour (PL XXXVII, fig. 22). In other cases there 

 is a manifest bifurcation of the fore-end of the prothallium 

 produced by the parting asunder and development of two 

 apical cells (PL XXXVII, figs. 17, 21). When the cells 



