414 XXX. THE SEED OF ANGIOSPERMS. 



what thicker above, obovate in profile, with a median dorsal 

 groove. At about mid-height of each achene, on its internal 

 (ventral) edge, is a short thread-like outgrowth, representing 

 the withered style, which, therefore, is ventral. For further study 

 we select an almost ripe etserio, place a single achene between the 

 two halves of a split cork, and draw the razor between these two 

 halves. We shall thus, without trouble, obtain tolerably median 

 longitudinal sections ; while cutting between the fingers presents 

 difficulties, as the spermoderm is very hard. At the same time we 

 will prepare some cross-sections between two pieces of cork. The 

 longitudinal sections we examine in water, to which we add a 

 little potash. For cross-sections pure water suffices. For the 

 study of the spermoderm by means of longitudinal sections the air 

 must be first driven out ; for this we can either lay the sections 

 for a short time in alcohol, or else place them under the air-pump. 

 We also lay some longitudinal sections in carbolic acid, and in this 

 way obtain figures which supplement the others in the most satis- 

 factory way. 



The longitudinal section, if correctly cut, presents the appear- 

 ance of the adjoining Fig. 150. We have first a comparatively 

 thick wall to the fruit, the pericarp, which in its surface is covered 

 by the epidermis (ep). This is, as our median longitudinal section 

 teaches us, a pretty sharply delimited part of the pericarp, and is 

 therefore distinguished as epicarp. To the epidermis follows a 

 parenchymatous tissue of approximately isodiametric cells, strongly 

 thickened, filled with air, and without intercellular spaces ; this 

 forms the mesocarp (m). To it follow several layers of elongated 

 sclerenchymatous elements the endocarp (en). A quite median 

 longitudinal section cuts, at the back of the pericarp, a mucilage 

 passage adjoining the epidermis, which is, however, only to be 

 seen well in an unripe pericarp ; in a ripe one, on the other hand, 

 it appears almost empty, and can scarcely be distinguished from 

 the neighbouring tissue. Longitudinal sections not truly median 

 may, on the other hand, expose a vascular bundle (v), which, 

 adjoining the sclerenchymatous endocarp, passes up at the back 

 of the fruit, in order to end in the lower half of the ventral edge 

 (at v*). Under the place of insertion of the withered style (st) the 

 ventral edge of the epicarp projects, and is here formed of elongated 

 cells. Adjoining these towards the interior we see, in favourable 

 cases, an air-passage (), which, continuing the pollen-passage 

 through the style, can be followed to the base of the cavity of 



