REPRODUCTION. 



229 



side of tlie ovule. The ovule is camjyylotrojyous or curved wlien its 

 own body is more or less curved. An anatropous ovule is shown in 

 the diagramatic figure of the angiospermous flower (Fig. 132); the 

 two other forms are represented in the accompanying figure 159, 

 (1 and 2). In the ovule, exclusive of funiculus, we distinguish the 



Fig. 159. (After Berthold and Landois ) 



body of the ovule (Jj) with the embryo-sac {c) and one or two 

 integuments; the latter {d, f) form the micropylar opening {e). 

 The hilum is the point where the funiculus {a) is attached to the 

 placenta ; the chalaza (A) is the zone at the base of the ovule from 

 which the tegumentary layers take their origin ; the rajyhe (seam) 

 is the line of union between the funiculus and ovule in anatropous 

 ovules. In semiauatropous (amphitropous) ovules the micropyle and 

 chalaza are about equidistant from the hilum (see Fig. 159, 3). 

 The anatropic and campylotropic ovules may further be apotropous^ 

 epitropous., or pleurotrop)ous, according to whether the ovule is 

 turned toward the base (apotropous), the apex (epitropous), or the 

 side (pleurotropous) of the ovary. Such variations in position are 

 intimately associated with the function of the pollen-tube. 



The Eiiihryo-sac. — Immediately before fertilization the embryo- 

 sac of angiosperms (monocotyledons and dicotyledons) contains, as 

 a rule, three cells near the micropyle and frequently three cells at 

 the opposite end. The latter have long been known as antipodal 

 cells, but no particular function had .been ascribed to them. Ac- 

 cording to more recent investigations, they very probably assist in 

 the processes of nutrition. Strasburger's investigations gave us the 

 most important results in regard to the nuclear divisions and fusions 

 which result in the formation of the six cells mentioned and the 

 secondary nucleus of the embryo-sac (see Fig. 132).* One of the 

 three cells near the micropyle takes ujd the role of the egg-cell. 

 The other two, which are known as the synergidce, are supposed 

 to assist in the process of fertilization. From the observations 



