THE HIGHER CRYPTOGAMIA. 253 



forming a wide covering over the places of attachment of 

 the older fronds and the ground beneath as in Flatyoerium 

 gr ancle, are entirely devoid of the irregularly-shaped, 

 fleshy, recurved frond. 



The vascular bundles of the horizontal stem are arranged 

 in a simple circle (PL XXXIV, figs. 8, 9) ; they form on 

 the upper side a polygonal net, and on the under side a 

 net with very narrow, parallel meshes. The arrangement 

 of the meshes in both nets is shown in PL XXXIV, figs. 

 10, 11. The vascular bundles pass to the fronds from 

 the angles of the meshes of the upper side. These bun- 

 dles anastomose frequently in the cortical layer of the upper 

 side of the stem. The vascular bundles of the roots originate 

 at the upper and lower terminal points of the narrow 

 meshes of the under side of the stem, the roots themselves 

 being arranged in transverse rows. Roots very frequently 

 penetrate into the substance of the decayed flat fronds, 

 where they ramify considerably. 



The cortical layer of cellular tissue which surrounds the 

 central vascular bundle of the root, exhibits an anatomical 

 peculiarity, having a remarkable analogy with what is seen 

 in the epiphytal Orchids and the Aroidese. The walls of 

 its cells, which become brown at an early period, are 

 thickened by a net-work of filaments. Narrow flat de- 

 pressions are seen between the very delicate threads of the 

 net (PL XXXIV, figs. 12, 12 J ). The outermost cellular 

 layer of the root of Platycerium, from which rootlets are 

 emitted, has the depressions, but not the reticulate threads. 



The apical cell of the end of the stem of Platycerium 

 alcicorne is two-edged, having the form of a strongly-com- 

 pressed cone. The arrangement of the surrounding cells 

 discloses the fact that the multiplication of the cells of the 

 terminal bud is brought about by the continuously repeated 

 formation in the cell of the first degree of septa inclined in 

 two opposite directions. A parabolical line drawn through 

 the middle point of the places of insertion of all the younger 

 fronds, cuts the upper surface of the apical cell of the stem, 

 not in its shortest but in its longest diameter. The top 

 cells of the young fronds have their edges, and not their 

 surfaces, tinned towards the ends of the stem, whose apical 



