326 BOTANICAL GAZETTE [MAY 
change of nomenclature which I would propose, therefore, refers 
only to the position of the archesporium, and not at all to the 
meaning of the term. It is simply this: let the term archespo- 
rium continue to be used as at present in descriptions of seed- 
plants, but let it be understood in the case of pteridophytes to 
signify the superficial cell or cells from which the spore-forming 
tissue is derived. In this way the difficulties which have been 
pointed out will all be met, and a better system of homologies 
can be made for sporangia in general. The archesporium will 
always occupy the same position relative to the primary meri- 
stematic regions, and will be the only part from which the spore- 
forming tissue arises. 
The nomenclature here proposed can be more easily under- 
stood by reference to the accompanying diagrams. igs. 69 and 
79 represent two early stages of the sporangium of a common 
fern (Pteris), but for the present purpose may be taken as typ- 
ical of any pteridophyte sporangium. The shaded cell (2) would 
be regarded as the archesporium; it divides into an inner fertile 
cell (f), from which all the spore mother cells are derived, and 
an outer cell (s) which gives rise to a large part of the sporan- 
gium wall. In some instances, as we have seen, the separation 
into fertile and sterile cells is not accomplished by the first divi- 
sion. In such cases there is no contradiction of terms, since all 
the spores arise from the archesporium. The final condition 1s 
the same in all cases, the difference consisting simply in the 
earlier or later sterilization of the wall region. ; 
fig. 71 represents a young microsporangium and fig. 73 * 
young megasporangium of anangiosperm. The outer layer (e),the 
epidermis, takes no part in the formation of the spore producing 
cells; @ is the archesporium, which usually, as in pteridophytes, 
divides into an outer sterile region (s) called the primary sg eal 
tum, and an inner fertile region (f) called the primary sporog- 
enous cell or cells (figs. 72, 74). The name primary tapetum 
was given to the sterile region to express its supposed function 
of giving origin to the true or functional tapetum. Enough ' 
now known of the origin of the true tapetum to enable us to say 
