598 ME. 8. LE M. MOOEE'S STUDIES 



this is especially the case with sections which have lain before 

 staining in chloriodide of zinc. 



Section of the endosperm in a plane parallel to the axis of 

 growth shows that it is composed of an epidermal layer greatly 

 thickened upon its outer side, beneath which lie several rows of 

 small cells with but slightly thickened walls. These walls react 

 with water very much as do the primary walls of the deeper- 

 lying large thickened cells, that is to say they swell up, but not 

 nearly to the same extent. With a low power (fig. 6) it is not 

 possible to see the primary wall of these cells, but it can be made 

 out with more or less ease right up to the epidermis with a ^--ln. 

 objective. These small cells are followed by layers of cells inter- 

 mediate in size between them and the underlying large cells. 

 In sections which have lain for twenty-four hours in chloriodide 

 of zinc, well-stained threads piercing the walls can be traced as 

 far as the epidermis (fig. 7) ; the protoplasm is therefore continuous 

 throughout the endosperm. 



In his memoir in the ' Philosophical Transactions,' Gardiner 

 contents himself with noticing the fact of continuity in the 

 endosperm of S. Ignatia without entering into any details. His 

 failure to observe the interesting differences between this species 

 and S. Nux-vomica was probably due to the use of chloride of 

 zinc alone, an excellent reagent for tissues which do not swell up 

 in it to any great extent, but much inferior to solution of iodine 

 iu alcohol in the case under notice. To this author belongs the 

 credit of first discovering an instance in which continuity through 

 the walls of endosperm-cells can be seen without special reagents 

 (Bentinckia Conda-panna) *. Here, however, comparatively high 

 powers are required, and as the walls are said to show merely an 

 " appearance of striation," it is clear that the fact cannot be 

 verified with the ease that it admits of when S. Ignatia is 

 examined f, 



Tangl I expressly says that the endosperm-cells of 8. potatorum 

 do not show continuity. The chief difference between these cells 

 and those of S. Nux-vomica is that their lumen is not round, but 

 produced tow r ards one or more of the faces of the primary wall, 



* Phil. Trans, memoir. 



t For this reason, and because of the low powers sufficient for the demon- 

 stration, the use of 8. Ignatia seeds is strongly to be recommended for class 

 purposes. * L, c. 



