FILICINE.E. 
411 
of which is subsequently developed a cylindrical vermiform shoot, which grows 
erect underground, is rarely and slightly branched, and elongates by means of 
a single apical cell. When the apex appears above ground and becomes green, 
it forms lobes and ceases to grow. The tissue of this prothallium is differen- 
tiated into an axial bundle of elongated, and a cortex of shorter parenchymatous 
cells, and the surface is clothed with root-hairs. With a transverse diameter 
of \ to i\ lines, it attains a length of from 2 lines to 2 inches. The pro- 
thallium of Botrychium Lunaria is. according to Hofmeister, an ovoid mass of 
firm cellular tissue, the greatest diameter of which does not exceed \ line, and 
is often much less (Fig. 287, Ä). It is light brown externally, yellowish white 
internally, and provided on all sides with sparse moderately long root-hairs. 
These prothallia are monoecious ; each one produces a number of antheridia and 
archegonia, which are distributed with tolerable uniformity over the whole of its 
upper surface, with the exception, in 0. pedunculosum, of the small primary tuber ; 
in Boirychiwn it is the upper side which chiefly bears antheridia. 
The Antheridia are cavities in the tissue of the prothallium covered externally 
by a few layers of cells, and in Ophioglossum only slightly projecting beyond the 
Fig. •2%-].— Botrychium Lu7iaria ; A longitudinal section of prothallium {X So), ac an archegoniuin, an an antheri- 
dium, w root hairs; B longitudinal section of the lower part of a young plant dug up in September (X20) ; st stem, 
* b' b'' leaves {after Hofmeister). 
surface. In this genus the mother-cells of the antherozoids originate by repeated 
divisions from one or two cells of the inner tissue (covered externally by one or 
two layers of cells) ; they form a mass of tissue of roundish form, and, as in 
Botrychium, give rise to the antherozoids, which are similar in form to those of the 
Polypodiaceae, but larger ; they escape through a narrow opening in the cover of the 
antheridium. 
The Archegonia are apparently developed in a similar manner to those of other 
Vascular Cryptogams. Mettenius saw in Ophioglossum instances in which they 
consisted of two cells, a superficial cell and one lying below it; this latter, he 
considered, became the central cell, the former producing the neck of the arche- 
gonium by dividing into four cells arranged crosswise, which then produce, by 
further divisions, four vertical rows each consisting of two or more cells, and thus 
form the neck. The wall of the ventral part which surrounds the central cell 
is formed by divisions of the cells of the prothallium which surround it; the 
ventral part is therefore completely imbedded, and only the neck, which is usually 
very short, projects above the surface. Mettenius asserts that in Ophioglossum a 
