SPORE-PRODUCING MEMBERS 455 
simpler, or reduction from a more complex type, may be a question 
for discussion; but it is clear that the gradually transitional forms do 
exist. 
As regards the first appearance of the sporangium, the essential parts 
of it, though not the whole body, are normally referable to a single 
parent-cell, and the first periclinal division delimits the sporogenous 
tissue (see Figs. 43, 44, p. 88). It appears that here all the sporogenous 
cells undergo the tetrad-division, and the nourishing tapetum, which is 
entirely derived from the surrounding tissue, makes 
its way inwards between the fertile cells! As 
regards vascular supply, a strand extends to within 
two cells of the base of the cavity, and there 
terminates. Finally, the dehiscence is as in 
Ophioglossum. It thus appears that the whole 
sporangium of Botrychium is of the Ophioglossum 
type, but it is more definite and specialised in its 
characters, and this goes naturally along with its 
smaller size, which is most marked in B. wirginianum. 
It has already been noted that the position 
of the fertile spike in Ae/minthostachys is similar 
to that of Ophioglossum: it may further be added 
that the origin of it is similar, and its structure 
in early stages not unlike. It appears first as an 
outgrowth on the adaxial side of the sterile frond, 
and it is curved over while young, so that the 
actual apex is pointed downwards: the whole of 
the spike is at first covered and protected by 
the segments of the sterile frond, which again are 
protected by the stipular sheath. Since then, as ; ; 
regards position, and the main facts of origin, Fes A aiinee cote 
the whole spike of Helminthostachys may be Se eis ome Gcetesed on 
régarded as homologous with the whole spike of aa Magnified. (ter 
Ophioglossum, a special interest will attach to the 
origin and development of those bodies which directly bear the sporangia 
in this genus, viz. the sporangiophores. 
Transverse sections of the fertile spike show at the lateral regions 
corresponding to the sporangiogenic bands in Ophioglossum, a fan-like 
tracery of the cell-walls, while the surface is covered by a rather regular 
series of deep cells: it is from these that the sporangiophores originate, 
as outgrowths of very irregular size and arrangement (Fig. 254 a). Growing 
first deeper, these cells divide by periclinal and anticlinal walls; the 
growth, however, is not uniform, but is localised at points so that 
rounded processes, often of very unequal size, make their appearance 
Fic. 254. 
1 Holtzman, Bot. Gaz., xvii., p. 214; Cardiff, Bot, Gas., xxxix., p. 340; also 
Studies, v., p. 197. 
