254 . BOTANICAL GAZETTE _ [APRIL 
from below was slight in amount, and had retained its original char- 
acter; while the epidermal cells had greatly elongated and had divided 
into epidermal and secondary fibrous layer cells (fig. 4). These sec- 
ondary fibrous layer cells resembled very closely at this stage those 
of the primary fibrous layer, and I sec no reason to suppose that they 
would not have developed fibers at the proper time. Here then the 
epidermis seems to have been more plastic under the injured spot 
than the deeper lying tissues. 
The fibers are developed in this layer shortly before the time the 
anther is to open, appearing on the side and bottom of each cell. 
Around the top, posterior, and bottom of the microsporangium there 
is a groove (figs. 5 and 7), and in the bottom of it the cells have no 
fibers and are quite thin-walled, so that they readily break, thus form- 
ing the line of dehiscence of the anther. As LECLERC DU SABLON (8) 
has shown for anthers in general, the opening is due to unequal 
shrinkage of the two walls of the fibrous layer. The outer wall being 
of cellulose, shrinks more on drying than the inner wall, which is 
strengthened by its lignified fibers. By this means the whole outer 
covering is bent upon itself and points directly toward the carpels 
(fig. 7); nearly all of the pollen adheres to these wings, and so is placed 
in the way of any insect that comes to visit the nectaries. The 
stigmas are ripe for pollination at the same time that the anthers open 
Any insect visiting many flowers in succession must scatter pollen 
promiscuously, so that there is sufficient adaptation to insure cTOss 
pollination, but no well-developed mechanism to prevent self-pollina- 
tion. Pollen is ripe and begins to be shed in the latter part of October, 
and is shed from that time on into the winter, as the flowers keep 
opening with each return of warm weather, even as late as January. 
OVULES AND EMBRYO SAC. 
The ovules show specialization of archesporial tissue at the tip of 
the nucellus before the integuments have begun to develop, but #t 
very difficult to distinguish archesporial cells, although there a 
to be several of these, each one cutting off a tapetal cell which divides 
repeatedly. The cells of this tissue then elongate in the direction of 
the long axis of the nucellus, and bury the mother-cells by some eight 
layers of cells in the nucellus. 
