THE OVULE. 



399 



stalk, the funicle (/) ; the free part of this is very short, the rest 

 of it has grown to the side of the ovule, forming upon it the raphe 

 (r). In the body of the ovule we note first of all the inner conical 

 mass of tissue, the nucellus (n). This corresponds with the 

 macrosporangium of Vascular Cryptogams. The nucellus is 

 encased in two integuments, an inner (ii) and an outer (ie). The 

 inner is developed on all sides right to the base of the nucellus, 

 the outer is wanting on the side of the raphe, since it joins on 

 both sides to the funicle. The inner integument leaves free a 

 narrow canal between its upper 

 edges, extending to the nucellus ; 

 this canal is known as the micro- 

 pyle. The funicle is traversed 

 by a vascular bundle, arising from 

 the placenta, which in many, but 

 not all, cases can be traced to 

 the base of the nucellus. The 

 tissue adjoining the base of the 

 nucellus, here distinguished by its 

 brighter colouring, is known as the 

 chalaza (ch). In the long axis 

 of the nucellus is noticeable a large 

 cell, forming quite a cavity ; this 

 is the embryo-sac (e). At its base 

 can be seen some globular cells, 

 which in Aconitum (and Ranuncu- 

 laceae generally) are very strongly 

 developed the antipodal cells (a). 



In specially favourable cases we can determine that they are three 

 in number. In the apex of the embryo-8ac we can also see a small 

 cell, which, however, is only recognisable in perfectly median 

 sections ; it is the oosphere, sometimes called the embryonic vesicle 

 or germinal vesicle (o). The ovule as a whole is described as 

 anatropous, i.e., turned back, because the body of the ovule does 

 not lie in direct continuation of the funicle, but appears laid by the 

 side of it, with one side grown to it, and the micropyle turned to 

 the base of the funicle. This form of ovule is by far the most 

 common in Angiosperms. If we now compare our preparation of 

 Delphinium (Fig. 144) with that of Aconitum (Fig. 145) we shall see 

 that the structure of the ovary and ovule in the two cases is quite 

 identical ; the distinction only is that in Delphinium, as very 



FIG. 145. Aconitum Na.pdlus ; 

 median longitudinal section of an ovule. 

 f, funiculus ; r, raphe ; v, vascular 

 bundle of the funicle ; ie., outer integn- 

 ment ; ii, inner integument ; n, nucel- 

 lus ; cJi , chalaza ; e, embryo-sac ; a, 

 antipodal cells ; o, the oosphere*; nc, 

 nucleus of the embryo-sac ; m, micro- 

 pyle ; *, wall of the ovary ( x 53). 



