PHANEROGAMS. .r>7 



Otherwise completely abortive staminal leaves \ In the Cycadese the pollen-sacs grow 

 singly or in groups on the under side of the relatively large stamens, often in large 

 numbers, resembling in position the sporangia on Fern-leaves. In the Coniferse the 

 stamens have still more lost the appearance of ordinary leaves ; they remain small, and 

 form several or only two relatively large pollen-sacs on the under side of the lamina 

 which is still distinctly developed. In Angiosperms the stamen is usually reduced to a 

 slender weak and often very long stalk called the Filament, bearing two pairs of pollen-sacs 

 at its upper end or on both sides beneath the apex, which are included as a whole under 

 the term Anther ; the anther therefore usually consists of two longitudinal halves, united 

 and at the same time separated by a part of the filament termed the Connecti've. The 

 two pollen-sacs of each half of the anther are contiguous throughout their length, and 

 frequently both halves of the anther are in close apposition. The separate pollen-sacs 

 then appear as compartments of the anther, which is in this case quadrilocular, in 

 contrast to those anthers (of rare occurrence) in which each half contains only a single 

 pollen-sac, and which are therefore biiocular. 



The Embryo-sac, the analogue of the macrospore, is the result of a very considerable 

 enlargement of an inner cell of the nucleus of the ovale, which itself corresponds to the 

 macrosporangium of heterosporous Cryptogams. The nucleus is a small-celled mass of 

 tissue of usually ovoid form, and enclosed, with a few exceptions, in one or two envelopes, 

 each of which consists of several layers of tissue. These envelopes or Integuments grow 

 round the young nucleus from its base, and form at its apex — where they approach and 

 often greatly overtop it — a canal-like entrance, the Mkropyle or Foramen, through which 

 the pollen-tube forces its way, in order to reach the apex of the embryo-sac. Very 

 commonly the nucleus, enclosed in its integuments, is seated on a stalk, the Funiculus ; 

 but this is sometimes wanting, and the ovule is then said to be sessile. The funiculus 

 is, with a few exceptions (Orchideae), penetrated by an axial fibro-vascular bundle which 

 usually ceases at the base of the nucleus. The external form of the ovule when in a state 

 for fertilisation is very various. Independently of outgrowths of various kinds at the 

 funiculus and the integuments, the direction of the nucleus (together with its coatings), 

 with respect to the funiculus, is of especial importance. The ovule is orthotropous when 

 the nucleus is in a direct line with the funiculus, and the apex of the nucleus is the apex 

 of the entire ovule. Much more frequently the ovule is anatropous ; i.e. the apex of the 

 nucleus, and therefore the micropyle which projects beyond it, faces the point of origin 

 of the funiculus, which runs along the side of the nucleus, so that the ovule appears as 

 if sharply curved at its base ; and the integuments (or at least the outer one), have 

 united in growth with the ascending funiculus, which, so far as this union is complete, 

 is termed the Rapf.^ ; the nucleus itself being in this case straight. Much less com- 

 mon is the campy lotropoiis ovule, where the nucleus itself (together with its coatings) 

 is curved ; its apical part, and therefore its micropyle, facing the base, but without any 

 lateral cohesion with the funiculus. These are, however, only the most striking forms, 

 which are united by transitional states. The place from which the ovules spring is called 

 the Placenta, and belongs to the axis of the flower, or more commonly to the carpels 

 themselves. The placentae often do not show any peculiar phenomena of growth ; but 

 more commonly they project like cushions, and may thus assume the appearance of 

 special organs, finally becoming detached from the surrounding tissue. While, after 

 fertilisation, both the endosperm and the embryo are undergoing simultaneous develop- 

 ment in the embryo-sac, the former most commonly increases considerably in size, and 

 supplants the surrounding layers of tissue of the nucleus (sometimes even of the inner 

 integument) ; and the tissue of the integument which is not displaced, or usually only 

 certain definite layers of it, becomes then developed into the Testa. If a portion of 



» [For instances of the production of pollen-grains in abnormal positions, even in ovaries or in 

 the ovules themselves, see Masters, Vegetable Teratology, Ray Soc. London 1869, pp. 182-188. 

 —Ed.] 



