Le Nee ee 
le Nae ee oe, ae 
oe 
To RO Pant pep nen ae eee 
inthe oute 
< aS hickory, walnut, &c., we find the female or pistillate 
stm 2 terminal peduncle, while the catkins of male or 
1884.] 
The Theory of Sex and Sexual Genesis. 783 
from variations in the conditions of the other factor. It should 
be remembered further that both factors are required to be pres- 
ent in the developmental process in the formative or initial stage 
of the development of all organs, the reproductive organs in- 
cluded, 
In the higher plants this initial part of the development is gen- 
erally effected at or within a very short portion of the extremity 
of each axis. But whether it is confined to this part or not, it is 
universally the case in “ perfect ” flowers that the pistils occupy 
the central position, with the stamens disposed around them. 
And that the central position is the one most favorable to cell- 
growth, and the outer position the one most favorable to cell- 
_ division, is shown by the fact that in the pith of exogenous 
plants the central cells are the largest—the cells decreasing in 
size from the center outward. The conditions on which this dif- 
rence depends are no doubt complex; but it is probably due 
mainly to the freer access of oxygen to the outer cells; since it 
has been shown that the oxygen consumed in these forming parts 
of plants is derived directly from the surrounding air, and is not 
j brought to them in the sap from other parts; while the nitrogen- 
US proximate compounds that enter into the formation of the 
‘xtending axis are derived mainly from other parts, and the whole 
Supply of the lower compounds of nitrogen necessary to the 
growth of the plant is taken in through the roots. The access of 
oxygen is required both for cell-growth and cell-division. But 
itis mainly to its nitrogenous constituents that protoplasm owes 
7 ts plasticity or instability as to state of physical aggregation ; 
and these Constituents are also chemically less stable than the 
other constituents. The more active respiratory changes induced 
r cells would, therefore, have the effect of causing 
_ to divide more rapidly than the central cells; or of prevent- 
mg them from growing to so great a size as that attained to by 
* Central cells before undergoing division. 
, dest onCecious plants it is the female flower, as a whole, that 
: i a part in which the conditions of cell-growth pre- 
the > and the male flower that develops from a part in which 
“onditions of cell-division predominate. In moncecious 
flowers are produced from lateral buds of the same 
