520 
PHANEROGAMS. 
The Ovules (macrosporangia), as we have already seen, are in the Podocarpese 
anatropous and furnished with two integuments; in the rest of Coniferge they are 
orthotropous and possess only one integument ; in the Cupressinese and Taxinese 
they are erect, in the Abietinese inverted, with the micropyle towards the base of 
the scale, to which the ovules are usually attached on one side. In these cases 
there is no funiculus, and the ovule consists only of the small-celled nucellus and 
one integument, which usually projects above it and forms a comparatively wide 
and long micropylar canal, through which the pollen-grains reach the apex of 
the nucellus, which is sometimes depressed (see Figs. 347, 348, 349, 352). Lateral 
outgrowths of the integument not unfrequently cause the ovule, and afterwards 
the seed, to appear winged on both sides, as in Callitris quadrivalvis (Fig. 352), 
Frenela, &c. The wing-like appendage of the seed of Pinus and Abies, on the 
other hand, is the result of the- detaching of a plate of tissue from the seminiferous 
scale, which remains attached to the ripe seed. 
\The Development of the Ovule and of the Embryo-sac. The development of the 
ovule begins in Taxus (according to Strasburger, Angiospermen und Gymno- 
spermen) with the division, parallel to the surface (periclinal), of a group of hypo- 
dermal cells at the punctum vegetationis of a lateral branch, and this is followed by 
similar divisions in the overlying epidermis. The rudiment of the ovule is sur- 
rounded by a projecting ring of tissue, also developed by the division of hypodermal 
cells, which is the first indication of the integument. The ovule elongates in 
consequence of growth and repeated cell-divisions, and consists internally of a 
number of longitudinal rows of cells, which have all been derived from the hypo- 
dermal layer, invested by several layers of cells which have been derived from the 
epidermal layer. The apical cells of these internal rows are distinguished by their 
size and by the granularity of their protoplasm ; they constitute the archesporium : 
they are surrounded by tapetal cells, but it is not clear whether the tapetum is 
derived from the archesporium or from the surrounding cells of the nucellus. One, 
but sometimes more, of the archesporial cells, usually the central one, divides so as 
to form three cells lying one above the other, and it is the lowest of these which 
enlarges and becomes the embryo-sac. The development of the ovule in Ginkgo 
biloba and in Podocarpus chinensis follows essentially the same course, as does also 
that of Thuja occidentalis. It will be observed that in these plants several embryo- 
sacs are frequently indicated at first, but only one attains perfect development. 
In the Abietineae [Larix europcEa, Pinus sylvestris and Pumilio) the multipli- 
cation of cells by the repeated division of the hypodermal and epidermal cells is 
much less considerable. The archesporium is unicellular ; as it elongates a small 
cell is cut off from it towards the free surface of the ovule, which is a tapetal cell ; 
the lower cell now divides into two, and of these two the upper divides again into 
two ; the lowest of these three cells developes into the embryo-sac. Only one 
embryo-sac is ever indicated in the group. 
A section of the young ovule of one of the Cupressineae, before the embryo- 
sac is developed, presents, as Goebel has pointed out, a considerable similarity 
the Conifers are really gymnospermous. In his most recent work on the subject (Die Angiospermen 
und die Gymnospermen) Strasburger accepts the view of the gymnospermous nature of the ovule.] 
