SPERM A PHYTES. 151 



the outer side of the sepals has breathing pores, but these are absent from 

 their inner surface, and from both sides of the petals. The walls of the 

 epidermal cells of the petals are peculiarly thickened by apparent infold- 

 ings of the wall (5), and these cells, as well as those below them, contain 

 small, yellow bodies (chromoplasts) to which the bright color of the flower 

 is due. The red specks on the base of the perigone leaves, as well as the 

 red color of the back of the sepals, the stalk, and leaves are due to a pur- 

 plish red cell sap filling the cells at these points. 



The filaments or stalks of the stamens are made up of very delicate col- 

 orless cells, and the centre is traversed by a single fibro-vascular bundle, 

 which is continued up through the centre of the anther. To study the 

 latter, thin cross-sections should be made and mounted in water. Each 

 of the four sporangia, or pollen sacs, is surrounded on the outside by a 

 wall, consisting of two layers of cells, becoming thicker in the middle of 

 the section where the single fibro-vascular bundle is seen (Fig. 81, H). On 

 opening, the cavities of the adjacent sporangia are thrown together. The 

 inner cells of the wall are marked by thickened bars, much as we saw in 

 the pine (Fig. 82, A), and which, like these, are formed shortly before the 

 pollen sacs open. The pollen spores (Fig. 81, /) are large, oval cells, having 

 a double wall, the outer one somewhat heavier than the inner one, but suffi- 

 ciently transparent to allow a clear view of the interior, which is filled with 

 very dense, granular protoplasm in which may be dimly seen two nuclei 

 (n, ni.), showing that here also there is a division of the spore contents, 

 although no wall is present. The spores do not germinate very readily, 

 and are less favorable for this purpose than those of some other mono- 

 cotyledons. Among the best for this purpose are the spiderwort ( Trades- 

 cantia) and Scilla. 



Owing to the large size and consequent opacity of the ovules, as well 

 as to the difficulty of getting the early stages, the development and finer 

 structure of the ovule will not be discussed here. The full-grown ovule 

 may be readily sectioned, and a general idea of its structure obtained. A 

 little potash may be used to advantage in this study, carefully washing it 

 away when the section is sufficiently cleared. We find now that the ovule 

 is attached to a stalk (funiculus) (Fig. 81, , /), the body of the ovule 

 being bent up so as to lie against the stalk. Such an inverted ovule is 

 called technically, " anatropous. " The ovule is much enlarged where 

 the stalk bends. The upper part of the ovule is on the whole like that of 

 the pine, but there are two integuments (i, n) instead of the single one 

 found in the pine. 



As the seed develops, the embryo sac (6r, sp.) enlarges so as to occupy 

 pretty much the whole space of the seed. At first it is nearly filled with 



