145 
gium, and it seems to me that too much stress has been laid upon 
this by some writers. 
In the earlier sporangia the first division walls are usually 
strongly oblique, but even here the first wall may be transverse 
(see Fig. 7, a.), as usually happens in the Polypodiaceze. Several 
oblique walls now arise which meet each other in such a way that 
the terminal cell has much the form of an ordinary tetrahedral 
apical cell. Soon, however, a wall is formed parallel to the outer 
wall of the terminal cell, and thus an inner cell (Fig. 7 Ga); male 
archesporium, is cut off. The archesporium is formed relatively 
earlier in the first formed sporangia which are almost sessile, 
while in the later ones, where they are more crowded, the pedi- 
cel is much better developed (Fig. 10). 
From the archesporium the tapetal cells (t.), are cut off in the 
usual way, and subsequently these divide by both radial and tan- 
gential walls into a large number of cells. For the most part 
there is but one set of tangential divisions, but sometimes there 
is a second one in some of the cells, so that at these points the 
tapetum is three cells thick. 
The central cell divides by an oblique wall into two cells and 
these each divide twice more, and sometimes some or all of the 
resulting cells may divide again, so that the whole number of the 
resulting spore mother-cells ranges from eight to sixteen. 
When the full number is complete the cells separate owing to 
the partial disintegration of the division walls, and, at the same 
time, the walls of the tapetal cells become completely absorbed 
and their contents form a mass of protoplasm in which the sepa- 
rated spore mother-cells are imbedded. These now increase 
somewhat in size and become globular as the pressure of the sur- 
rounding cells is removed. The sporangium has now increased a 
good deal in size and the spore mother-cells do not completely 
fill it. . 
In fresh sporangia the tapetal-cells appear completely disor- 
_ ganized, but when stained sections are examined it is evident 
enough that the protoplasm and nuclei of the cells persist un- 
changed, and the further development shows that the protoplasm 
and nuclei of the tapetum probably play an important part in ya 
further growth of the spores. - ee ree 
