Stee yr 
1913] BURLINGAME—ARAUCARIA BRASILIENSIS 105 
beginnings of two sporangia adjacent to one another but in differ- 
ent rows. 
Occasionally one can distinguish what appears to be the 
archesporium almost as soon as the sporangium itself is recog- 
nizable, but much more commonly it cannot be detected until the 
sporangium is 12-15 cells in length and 8-10 cells wide (plate figs. 
4, 5, 6). Not infrequently sporangia as far developed as that 
shown in plate fig. 7 do not show any differentiation of sporogenous 
cells. Ordinarily one can recognize all the primary regions of the 
sporangium at this stage. The cells of the tapetum seem to be 
derived more or less indifferently from those of the wall layers 
outside, or from derivatives of the inner and presumably sporoge- 
nous cells. However, I should not like to be too dogmatic in regard 
to this. Multiplication of cells continues until the sporogenous 
tissue consists of a mass some 20 cells in cross-section (plate fig. 8) 
and 40-50 cells long. The tapetum remains one or two cells thick, 
the ultimate cells being elongated radially and retaining their 
position and structure till some time during the development of the 
male gametophyte. At this time there are 4-6 layers of wall cells 
radially flattened, with very little cell contents. The epidermis is 
at this time filled with a densely staining substance, resembling 
tannin in its staining reactions, and presenting a very effective 
barrier to the ready penetration of the ordinary reagents. In the 
further development of the sporangium the contents of these epider- 
mal cells disappear, and the radial walls, seen in a cross-section of 
a sporangium, thicken in the fashion of a fern annulus, except at 
the point of future dehiscence. The wall cells are eventually 
crushed and more or less destroyed and the tapetum finally dis- 
integrates (text figs. 8 and 9). 
Sporogenesis 
After the last division of the sporogenous cells, the mother cells 
begin enlarging, until at the prophase of the heterotypic division 
they have attained a diameter more than twice that of the sporoge- 
nous cells. This eight or ten times increase of volume is largely 
water, the cytoplasm becoming greatly vacuolated as the growth 
increases. There is a corresponding enlargement of the nucleus, 
