49» PHANEROGAMS. 



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 nucellus from its base (the chalaza), and form at its apex — where they ap- 

 proach and often greatly overtop it — a canal-like entrance, the Micropyle or Foramen^ 

 through which the pollen-tube forces its way, in order to reach the apex of the embryo- 

 sac. Very commonly the nucellus, 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 

 point of attachment of the ovule to the funiculus is termed the hilum. The funiculus 

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

 usually ceases at the base of the nucellus. 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 nucellus (together with its coats), 

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

 the nucellus lies in the same straight line as the hilum and chalaza, which coincide 

 in position, and the apex of the nucellus is the apex of the entire ovule. Much more 

 frequently the ovule is anatropous, i.e. the apex of the nucellus, and therefore the 

 micropyle which projects beyond it, lies close to the hilum, the chalaza being at the 

 opposite end, and the funiculus runs along the side of the nucellus, so that the ovule 

 appears as if sharply curved at its base ; 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 Raphe; the nucellus itself being in this case straight. Much less com- 

 mon is the campy lotropous ovule, where the nucellus itself (together with its coats) is 

 curved; its apical part, and therefore its micropyle, chalaza and hilum, lie close to- 

 gether at its base. These are, however, only the most striking forms, whJth 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 nucellus (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 T:esta. If a portion of 

 the tissue of the nucellus, filled with food-materials, remains unchanged until the seed 

 is ripe, it is distinguished as the Perisperm ; its food-materials, although lying outside the 

 embryo-sac, are consumed by the embryo during germination ; and the perisperm may 

 then act physiologically as the representative of the endosperm \ The seeds of 

 Piperaceae, Zingiberaceae, and some Nymphaeaceae contain both endosperm and peri- 

 sperm. Sometimes the ovule, during the period of its development into a seed, is 

 enveloped from below by a new coating, which usually itself surrounds the tough testa as 

 a soft mantle, and is termed the ^ril. Of this nature is the red pulp which surrounds 

 the hard-shelled seed of the Yew ; and the origin is the same of the so-called ' mace ' of 

 the nutmeg, the seed of Myristica fragrans. 



If we now turn our attention to the morphological nature of those structures from 

 which the ovule immediately springs, we find a considerable variety. Only rarely does 

 the orthotropous ovule appear as the prolongation or terminal structure of the floral 

 axis itself, so that the nucellus forms directly the vegetative cone of the latter, as in 

 Taxus and the Polygonaceae. It is more usual for the ovule to grow laterally on the 

 floral axis, thus corresponding in position to a leaf, as in Juniperus, Primulaceae, and 



^ [The endosperm and perisperm are generally both included in English text-books under the 

 term 'albumen,' a term which should by all means be avoided, as conveying the idea of a definite 

 chemical composition, whereas that of the endosperm varies greatly.] 



