BY W. A. HASWELL, M.A., D.SC. 1031 



less completely united into a ring. Outside of the vessels is the 

 phloem which tills in the spaces between the groups of vessels so as 

 to give the whole bundle a cylindrical form. The centre of the 

 bundle is occupied by a strand of sclerenchyma. In the younger 

 branches the sclerenchyma disappears, and the vessels are arranged 

 in a flattened strand surrounded by phloem. There is no brown 

 matter, or only isolated spiral lines of it, and the endodermis is 

 only distinguishable by its thinner cell-walls. The walls of the 

 parenchyma cells are considerably thickened towards the periphery 

 where their cavities are filled with chlorophyll granules. The 

 epidermis has a very thick laminated cuticle. Stomata are 

 abundant on the stem between the ridges, but there are hone on 

 the leaves nor on the ridges. The mesophyll of the leaves and of 

 the leaf-ridges has the same peculiar form as in Tmesipleris ; 

 numerous short blunt processes from the walls of the cells articu- 

 lating with corresponding processes from neighbouring cells, 

 numerous anastomosing intercellular spaces being thus formed. 



The wall of the sporangium has the same structure as in 

 Tmesipteris, except that there are no vessels in the septa. 



The spores, of which each sporangium contains a very large 

 number, are of a rather narrow oval outline with a nearly straight 

 ventral, and convex dorsal border. Along the ventral border 

 runs a narrow line which mai'ks the line of dehiscence of the two 

 halves or valves into which the exospore splits to allow of the exit 

 of its contents. 



It is not to be wondered at, taking into account the want of 

 success which has hitherto always followed attempts to cultivate 

 the spores of Lyco2}odium, that in repeated experiments with the 

 spores of both Psilotum and Tmesipteris under various conditions 

 of substratum, light, heat, and moisture, I have hitherto failed to 

 rear the prothallia of these genera. 



