Vascular Strands of Fern-Seedlings. 123 
(Eudorina- like) type, and subsequently giving rise to the fully 
differentiated Plcodorina by growth of the cells in the posterior half 
of the colony. Shaw (loc. cit.) has shown, that in the young colonies 
of P. cnlifomica the two kinds of cells are not distinct in size. 
A more detailed study of the material may enable me to arrive at 
a definite conclusion on this point. 
University College, London. F. E. FRITSCH. 
May, 1904. 
ON THE ARRANGEMENT OF THE VASCULAR 
STRANDS IN THE “SEEDLINGS” OF CERTAIN 
LEPTOSPORANGIATE FERNS. 
[Preliminary Notice.] 
F OR some time past the writer has been engaged upon the 
detailed study of the development of the vascular system in 
a considerable number of Ferns, mostly belonging to Polypodiaceae. 
The work has reached a stage of completeness warranting the 
issue of a preliminary notice, and it is hoped that a full account 
may soon be published. 
The plants examined were representatives of some twenty 
genera, viz: Osmundncene : Todea. Cyatlieaceae : Alsophila, Dick- 
sonia. Polypodiaceae : Adiantum, Aspidium, Asplenium, Blechnum, 
Davallia, Doodia, Doryopteris, Lastraea, Lomaria, Nephrodium, 
Nephrolepis, Notochlaena, Onychium, Polypodium, Polystichum, 
Pteris. Hydropteridcae : Pilularia. 
On the whole, the earlier stages in the elaboration of the vas¬ 
cular system have been found to be very constant in all the types 
examined. The primary roots were always of the well-known diarch 
character, the transition to the solid protostele taking place in the 
manner rendered so familiar by the work of Gerard, Leclcrc du 
Sablon, Jeffrey and others. At a slightly higher level, we have a 
few parenchyma cellsappearing at the centre of thexylem rod, quickly 
followed by the differentiation of sieve-tubes, the appearance of the 
latter elements heralding the immediate formation of the first leaf- 
trace. The first few leaf-traces do not involve the formation of any 
real leaf-gaps; in other words the ground-parenchyma does not 
“ encroach upon ” the vascular tissue, but merely replaces the xylem 
and phloem thus temporarily interrupted by the departure of the 
leaf-trace. Subsequent changes seem to indicate the occurrence 
of two closely related types in Polypodiaceae, 
