In the PHANEROGAMS the =Microsporangia= are termed =Pollen-sacs=. They take their origin from a large group of cells, which, in the Angiosperms, lie immediately beneath the epidermal cells of the anther. In the developed, but not yet mature, sporangium (pollen-sac) there are to be found: (as in the Vascular Cryptogams) (1) an internal group of mother-cells which give rise to the _pollen-grains_ (_microspores_), in this case also formed in tetrads; (2) a group of cells surrounding these, of which the internal ones form a _tapetal layer_, similar to that in the Vascular Cryptogams; the tapetum and some of the cells surrounding it in this group, become dissolved before maturity; the more external ones, on the other hand, are provided with peculiar thickenings, and form the “fibrous” layer by the aid of which the dehiscence of the anther takes place; (3) an external layer, the epidermis, enclosing all the other layers (Fig. 247). In some Coniferæ (_Cupressus_, _Thuja_, and several species of _Juniperus_) the microsporangia (pollen-sacs), which are situated on the under side of the stamen, are covered by a thin structure which seems to be a continuation of the lamina and which is supposed to be homologous with the indusium of the Ferns. [Illustration: FIG. 248.--Development of the ovule in the Red Currant, _Ribes rubrum_, arranged alphabetically in the order of development. _A_ Is the youngest stage, _E_ the oldest. _ii_ Inner integument; _ie_ outer integument; _nc_ nucellus; _m_ archespore (mother-cell of the embryo-sac).] =The Ovule= in the Phanerogams arises most frequently on a projecting portion of the carpel, termed the _placenta_. The ovules (compare the sporangium of the Eusporangiatæ and especially the pollen-sac) take their origin from a _group of cells which lies beneath the epidermis_ (Fig. 248 _A_, _B_). First of all a small papilla is formed, which is later on provided with a _vascular bundle_ and becomes the _funicle_; this probably has the same value as the projections (“placenta”) on which the sori in the Ferns are attached. Only _one_ =macrosporangium= (_nucellus_; Fig. 248 _nc_) is developed at the apex of the funicle. This arises by a process of cell-division exactly corresponding to that by which the pollen-sacs are formed (Fig. 248 _C-E_), with this difference only, that while a great _many_ cells may be distinguished in each pollen-sac, which forms pollen-grains by tetrad-division, only a few are found in the ovule, and all these moreover are _suppressed, with one single exception_ which developes into the =macrospore= (=embryo-sac=) without undergoing a division into tetrads. The wall of the embryo-sac, in the Gymnosperms, may be thick and divided into two layers and partly cuticularized, as in the spores of the Cryptogams which are to be set free. In the Angiosperms, on the other hand, the wall is extremely thin.