1918] BUCHHOLZ—PINUS 221 
due to pleurality of archegonia.’ In Pinus one usually finds both 
types associated in the same ovule, and cleavage polyembryony 
always occurs in the several species of Pinus that were investigated. 
It is probably a constant feature of this genus. 
4. The rosette consists of a group of embryo initials which 
usually produce embryos. Rosette embryos, like 3 of the 4 primary 
embryos, are always aborted. 
5. Each embryo of a system may be traced back to an initial 
cell, one of the first completely walled cells of the proembryo. The 
8 embryos formed by the cleavage of the egg are therefore definitely 
organized from the time of the last free nuclear division. 
6. A further splitting of one of these 8 embryos into “twins” 
was not found to occur in Pinus. In rare cases 2 matured embryos 
were found in an ovule, but they were very unequal and due 
simply to the incomplete dominance of a single embryo. 
7. The early embryo develops by means of an apical cell which 
exists from the time the first walls appear in the proembryo. This 
apical cell persists for a considerable period, being still recognizable 
in embryos of 500-700 cells. 
8. The apical cell represents a primitive fern character, which is 
recapitulated in the embryogeny of Pinus. 
9. Less than 4 primary embryos per archegonium may be pro- 
duced in case one of the embryo initials, or the early apical cell, 
disorganizes. 
10. The suspensor is formed by the elongation of cells in the 
basal portion of the embryo, a process that begins with the elonga- 
tion of the first apical cell segment and continues until the maturity 
of the embryo. 
11. Suspensor cells or embryonal tubes never divide after 
elongation, but rosette cells may elongate and later divide in form- 
ing the rosétte embryos, showing their greater potentialities and 
their distinctness from the suspensor cells which they resemble. 
12. Considerable variation occurs in the first secondary sus- 
pensor divisions, also in the time of appearance of the first oblique 
walls formed by the apical cell; both are doubtless related to the 
time of separation of the embryos. 
13. Cleavage polyembryony is a primitive character which 
Pinus, Sciadopitys, Actinostrobus, and doubtless other genera have 
