THE HIGHER CRYPTOGAMTA. 249 



common in this species. They occur very frequently in 

 plants which grow in places having a comparatively small 

 amount of moisture, as is the case usually in an open 

 plain. The frond-arrangement oscillates unsteadily be- 

 tween \ and \. Similar deviations occur in Polypodium 

 Dryopteris. 



The walls, by whose appearance in the first cell of the 

 rudimentary frond the formation of the stipes commences, 

 are radial, not tangential to the axis of the stem (PI. 

 XXXIV, fig. 4), agreeing in this respect with those of 

 Aspidium jilix-mas, and differing from those of Pteris 

 aquilina. At the slender ends of the stems of Nipliobohs 

 rupestris and N. splendens, the development of the scales 

 may be very conveniently traced. This development takes 

 place at some little distance underneath the apical cell of 

 the stem. The formation of the scales begins at a distance 

 of eight cells from the top, reckoning downwards, by the 

 formation of a papillate protuberance of the free outer wall 

 of a cell of the circumference (PL XXXII, fig. 9). The pro- 

 tuberance is soon cut off from the original cell-cavity by a 

 transverse septum. The appearance of a new transverse 

 septum then divides the cell, which is already much flattened 

 laterally, into an upper and a lower cell (PI. XXXII, fig. 10). 

 Repeated transverse divisions, not only of the apical cell, 

 but also of the interstitial cells (PI. XXXII, figs. 11, 12), 

 transform the rudiment of the frond into a short series of 

 low cells with an elliptical basal surface. The phenomena 

 which become visible from these divisions, and especially 

 the gradual dissolution of the primary nucleus of the divid- 

 ing cell and the appearance of two new nuclei in its place, 

 are precisely the same as those which are observed in the 

 multiplication of the cells of the hairs of phaenogamous 

 plants (PL XXXII, fig 11). 



The cells of the lower portion of the young frond now 

 divide by longitudinal septa which coincide with the me- 

 dian line of the frond. These longitudinal septa are per- 

 pendicular to the surface of the frond, like the walls of 

 almost all the cells which take part in the formation of the 

 scales of ferns. The division progresses from the base 

 of the frond towards its apex, extending in Mp/todoius ru- 



