2 00 The Ohio Naturalist. [Vol. VIII, No. 1, 



On September 2d the first division of the functional mega- 

 spore has occurred. The resv:lt is the two-celled embryo-sac 

 (Fig. 16). The three non-functional megaspores are also appar- 

 ent as they have not completely disorganized at this time. 



A process of dissolution of the nucellus begins about this date 

 which makes the study of the embryo-sac almost impossible. The 

 cells of the sporangium wall begin to break down, leaving frag- 

 ments of cytoplasm and especially of nuclear material scattered 

 around the sac. This is Avell shown in the four-celled em.bryo- 

 sac of September 8th (Fig. 17). It will be noted from this figure 

 that only the apical cells remain intact. The drawing does not 

 show the full amount of disorganizing material, as that of the 

 median portion has been left out in order to show better the four 

 nuclei of the embryo-sac. 



From material collected September 24th, 1906, it was not 

 possible to make out the cell stage of the embryo-sac That 

 taken September 26th, 1905, was thought to be the four-celled 

 sac. The ovules of all of the material from October 12th, 1905, 

 to January 29th. 1906 were so dense with disorganizing cells that 

 the stage of the embryo-sacs could not be determined. 



Material collected on February 2Sth contained embryo-sacs in 

 the eight-celled stage. As this is before cell activity begins in 

 the spring it is quite probable that the sac passes the winter in 

 the eight-celled stage. If this is the case then we have the 

 completion of both the male and female gametoph3''tes before 

 the winter rest begins. 



Nearly all of the cells of the nucellus are used up by Api^jl 

 30th. This leaves the eight-celled embryo-sac lying within the 

 integtiment. The two synergids at the apex of the sac are long, 

 slender, pointed cones, and project far up into the micropylar 

 canal (Fig. 20). They are covered by quite a number of irreg- 

 ular longitudinal ridges. This part of the sac is very dense and 

 always takes a deep stain. 



On May 7th the epidermal columnar cells of the stigma begin 

 to elongate. By May 14th these same cells are club-shaped. 

 The conducting cells of the stylar canal are cuboidal and are 

 very glandular in appearance. 



The eight-celled stage of the embryo-sac persists till about 

 the 21st of May. It has greatly elongated by this time (Fig. 18). 

 The three intipodal cells are very small and lie in the extreme 

 lower end. A very few, widely scattered, nuclei of the nucellus 

 are to be seen in the sac. The definitive nucleus lies close to the 

 egg, just below it in Fig. 18 and by its side in Figs. 19 and 20. 



POLLENATION AND FERTILIZATION. 



Pollen was collected May 15th, 1906, by simply jarring the 

 flower against the slide. This was the beginning of the shedding 

 of the pollen, for microsporangia of May 14th still contained the 



