T. S. COBBOLD ON TTTF] EMBRYOLOGY OF ACHIMENES BICTA. 21 



from the placenta and directed towards the micropyle of an adjacent 

 ovule. On referrmg to my original notes I find it described as " an 

 enlarged cell containing granules, and somewhat resembling pro- 

 cesses that Wilson had previously figured as occurring in Statice 

 armeriar However, at a discussion which took jDlace at the Linnean 

 Society, a few years ago, I stated my belief that the process in 

 question was neither more nor less than the projecting end of a 

 solitary pollen tube. To be sure, as Sachs has pointed out, some 

 plants {Euphorbias for example) have special hairs developed in the 

 interior of the ovary, which serve as aids in directing the pollen 

 tube to its destination. The cell-process in Briigmansia was destitute 

 of any partition, and could not be confounded with any ordinary 

 vegetable hair even of the unicellular type. In Achimenes, whilst 

 the outer integument of the ovary is everywhere welt supplied with 

 finely pointed hairs, whose large cells often contains a brilliantly 

 coloured protojolasm, the inner integument or lining membrane 

 consists of a single layer of muriform parenchyma, the cells of which 

 measure about ^\-f^' in length, by -~^" in breadth. 



By gently scraping the slender, club-shaped utriculi of the 

 stigmatic lobes of Achimenes with a penknife, it is easy to remove 

 the germinating grains with portions of their tubes attached. The 

 ovary of Achimenes contains numerous anatropal ovules. In an 

 already advanced stage of growth, but prior to impregnation one 

 sees a large central dark mass of cells forming the so-called nucleus 

 or tercine, as I prefer to call it, using Mirbel's term to prevent con- 

 fusion. Within this mass, at the lower part, one or more of the 

 central cells differentiate to form the embryo-sac, which latter, 

 growing towards the apex of the tercine, expands at the summit so 

 as to present, in profile, a spoon-shaped figure, with the short 

 handle directed towards the chalaza. In actual shape the form of 

 the sac may be fitly compared to the bulb or lower end of a 

 thermometer turned upside down. The thickness of the tercine 

 prevented my observing the nucleus of the embryo-sac itself, and 

 after the sac had acquired its characteristic shape, it showed 

 merely a few fine granules in the interior, or, in addition to 

 these, either a solitary embryonal vesicle (oospore) near the apex, 

 or two vesicles placed side by side. In this situation the vesicle 

 was occasionally obscured by the expanded end of the applied pollen 

 tube, but in one instance it could be seen through the enlarged ex- 

 tremity of the tube. More commonly the applied coecal end of the 



