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Transactions. 



into a tier of four cells not separated by cell-walls (fig. 10). Both ovules in 

 the bud showed exactly the same stage in development. This stage was 

 also seen in other buds, but all were male. No corresponding stage was 

 observed in female buds of the same date. The female buds also showed 

 that both ovules were at the same stage in development until the opening 

 of the flowers, when often one is aborted. In flowers with three carpels 

 one or two may be aborted or all may mature. In any case, all the carpels 

 are developed, and the fruit appears normal externally. 



Fiu. 10. — Longitudinal section of ovule in male flower. 

 Fig. 11. — Cross-section of same stage. X 175. 



Archesporium. X 175. 



The nucellus finally consists of a single row of cells, regular and rectangular 

 in both cross and longitudinal sections. It is drawn up, the micropyle 

 leaving the embryo-sac exposed. The contents of the embryo-sac in these 

 early stages were not made out. There was, however, a possible indication 

 of synergidae and a probable ovum, though there was no appearance of 

 antipodal cells. 



Hypostase. 



At the base of the embryo-sac, supporting it and interrupting the 

 nucellus, was found a funnel-shaped structure consisting of cells resembling 

 those of the nucellus, but staining less deeply with Erhlich's acid haema- 

 toxylin. They had clear walls and large nuclei (figs. 12 and 13). This 

 structure was identified with the hypostase which Van Teighem notes in 

 Rosaceae and allied polypetalous dicotyledons. He says, " It consists of 

 a small cupule of isodiametric cells which have strongly lignified but not 

 much thickened membranes, and is found in the nucellus below the embryo- 

 sac, its object being to arrest the longitudinal growth of the embryo-sac 

 and endosperm towards the base of the ovule. Owing to its strong ligni- 

 fication, it resists the various diastatic agencies at work during the formation 

 of the embryo and endosperm, and for the same reason is incapable o- 

 growth. Hence it appears in the ripe fruit exactly as in the pistil, but, being 

 relatively much smaller, it is difficult to find. By arresting the basal de T 



