106 THE SPORANGIUM DEFINED 
It remains to consider the archesporium, and the sporogenous group 
and spores which arise from it. An archesporium, in one form or another, 
is a necessary constant in the development of a fertile sporangium: the 
form, the limits, the mode of origin and of later segmentation which it 
shows, may vary, as indeed is seen to be the case in the different sporangial 
types; but whatever its variations may be, it is in the archesporium, and 
in the sporogenous cells which it produces, that we see the essential feature 
of the sporangium. It will be necessary, then, to examine it carefully, 
and to see how far it is possible to attach a definite meaning to it. 
The term archesporium was introduced by Goebel,! and defined as 
follows: “In the Vascular Cryptogams, as in the Phanerogams, the 
spore-producing tissue may be universally referred as regards its origin 
to a cell, a cell-row, or a cell-sheet:—I designate these original parent 
cells of the sporogenous tissue as the archesporium.” To this he added 
that “in all Vascular Cryptogams examined an hypodermal archesporium 
exists,” thus definitely localising it in a position comparable to that 
in the Spermophyta. He remarks, however, later that he does not lay 
special stress upon the archesporium being always a cell-row or cell-sheet, 
and contemplates it as possible that sometimes the development may 
proceed otherwise than by the appearance of an archesporium of the 
form described. An examination of all the types of sporangia of living 
Pteridophytes has shown that this is the fact: a considerable number of 
cases have been observed in which the archesporium is not hypodermal, 
in that it is not defined by a single periclinal wall of the parent cells 
involved. The existence of many exceptions among Eusporangiate 
Pteridophytes suggests a reconsideration of the archesporium. We may 
enquire whether a definite meaning is attached to the term, and if so, 
whether that meaning is of general application. 
The effect.of Goebel’s anvestigations on the sporangia of Pteridophytes 
was to extend downwards from the Phanerogams the demonstration of a 
formative cell or cells to which the origin of the spores may be ascribed. 
Before 1880 it was held that a mass of cells within the young sporangium, 
showing irregular divisions, took upon them the character of a sporogenous 
tissue: Goebel’s results led him, as we have seen, to the statement that 
the spore-producing tissue can be referred as regards its origin to a 
cell, a cell-row, or a cell-sheet, which can be distinguished very early 
by the nature of its materials from the rest of the cell-tissue. This 
archesporium * was successfully recognised in certain cases, and the 
tendency of the time was to expect similar success in all cases. Thus a 
special significance came to be attached to these cells, quite apart from 
that of the surrounding tissues, as being predestined from the first to the 
important function of spore-production. 
The location of the archesporium in the Phanerogams was found to 
be consistently hypodermal: in a somewhat strained sense the same was 
1Bot. Zert., 1880, p. 545 ete. 
Ye 
