OF FERNS FROM THEIR SPORES. 121 
course of development in a comparatively short space of time, we have them coexistent in 
every condition of their development in prothallia which are fully formed. When anthe- 
ridia appear on very young prothallia, composed of a single row of cells, or at most of a 
double row in the upper part, they present themselves as productions from the margins, 
the outer side of one of the cells giving origin to each antheridium. But as soon as the 
prothallium has acquired anything like a flattened form, by the transverse expansion of 
the anterior end, the antheridia are formed almost exclusively upon the inferior surface, 
that surface in contact with the soil upon which the plant grows. They appear first upon 
the older cells of the central region, and gradually spread forward as the prothallium 
grows, but appear seldom to extend beyond a certain distance from the centre, occurring 
in greatest number about the central cushion-like protuberance above described. 
It has already been stated that they occur upon the progeny of the proliferous barren 
prothallia; in some cases I have found these branching at their edges and bearing anthe- 
ridia in a very abnormal position, at the ends of projecting cellular processes (figs. 27-32); 
this, however, afforded great facility for observing the internal structure of these organs, 
and checking the results obtained by observations upon sections. 
The first sign of the production of an antheridiwm consists in the elevation of a globular 
protuberance from the lower, free surface (or in the young prothallia from a lateral 
surface), forming at first a kind of globular pouch (fig. 17), in which are seen at first a 
few chlorophyll globules, which afterwards vanish and give place to a collection of light 
yellowish, mucilaginous contents, slightly granular. A septum is soon formed, shutting 
off this budding cell from that which gives origin to it, and as it becomes elongated 
another cross septum often appears, a little higher up (figs. 21 & 29, &e.), so that the 
structure then consists of a basal cell forming a peduncle,'as it were, for the proper anthe- 
ridial structure. This occurs most distinctly in marginal antheridia (figs. 27-32). 
The antheridial structure, at first consisting of a simple cell, exhibits a considerable 
eollection of protoplasm occupying the greater part of its cavity ; but this portion soon 
becomes defined by a cireular wall, which makes its appearance simultaneously all round 
the central eontents, converting the simple cell into a compound organ, Ang of a 
central cell surrounded by an annular cell; while a horizontal septum is formed above 
and at right angles to this, eutting off a new cell, convex above and flat at the surface, in 
n ith the contents. | 
at aie produced on young prothallia, the enveloping tubular cell ne 
the central cell (the parent-cell of the sperm-cells) does not always undergo m = 
division, but in fully developed specimens (when the basal, peduncular cell is — a sig 
the tubular cell appears to be divided into two by a horizontal septum running — 
This wall is seen most clearly in old antheridia which have discharged their contents 
ae cell meanwhile acquires an increased quantity of protoplasm, which irc 
appears to become more dense; these contents by their increase cause the se the " | 
to bulge out in all directions, and at a certain stage they seem to press so muc "penne 
inner wall of the annular cell, forming the boundary of the central cell, as to push it quite 
against the outer wall, in fact so as to flatten the boundary cell, and for the time to efface 
