188 BOTANICAL GAZETTE [SEPTEMBER 
are accurate and most of them still useful. He denies the existence 
of an apical cell in all but the Cupressineae, where he found a 
definitely organized apical cell in the early embryo. In Pinus and 
other Abietineae he finds this stage omitted or not constantly 
present, an indication that these are less primitive than the Cupres- 
sineae. In the further differentiation of the embryo he goes 
into greater detail than any previous worker. In Pinus and Picea 
the plerome tip of the root is set off about o.15 mm. from the apex 
of the cylindrical mass of cells which is now about o.5 mm. long, 
measured to the point where the cells form suspensors. In the 
account, which he says is practically the same for all the conifers, 
the stem tip meristem is next in appearance, followed by the 
cotyledonary primordia which arise in a circle about this point. 
His description of the cotyledon and stem tip development is sub-. 
stantially the same as that of SCHLEIDEN (36). At this stage 
of development the embryo reaches the lower end of the endosperm, 
and further growth and elongation bring the radical end of the 
embryo back to the place of origin of the suspensor. 
STRASBURGER states that the number of embryos beginning 
development may be as high as 20, all but one of which abort in 
various early stages of development. In Picea vulgaris he finds 
that the 4 rows of cells of the proembryo do not separate, but all 
4 of the embryonal cells at the tip of the suspensor contribute to 
the formation of 1 embryo. 
The accounts, by the early workers, of the proembryo stages 
differ widely. ScHacut (35) shows correctly the completed pro- 
embryo when it consists of 4 tiers of 4 cells each with the upper tier 
open to the egg. STRASBURGER (38, 39) attempted to explain 
the stages between fertilization and this completed proembryo, 
but, like other early workers, he failed to recognize the nature and 
extent of the free nuclear divisions. CHAMBERLAIN (5) described 
some details in the development of the proembryo, and later 
CouLTER and CHAMBERLAIN (9) figured a more complete series 
of these stages. Frrcuson (13) added still more, working on 6 
genera of Pinus, and found, as did Mrvyaxe (28) in Picea, that the 
upper tier of 4 cells, in the 8-celled proembryo, divide before the 
lower. Later, Kirpant (19) found both orders of division in 
