426 MORPHOLOGY. 



absorbed, at least on the outer side, by the pressure of the grow- 

 ing endosperm, so that the endosperm exhibits a convex- concave 

 form, the concavity of which receives the remaining portion within 

 it, whilst the convex surface is quite naked. This remarkable 

 process takes place in that section of the species of Veronica which 

 has been named cochlidiospermce. 



More frequently the integuments remain, at least as a thin 

 pellicle, readily falling into shreds, but adhering to the endosperm, 

 as in many Rubiacece, especially in the Coffee. Usually they form 

 a closed envelope to the perisperm, endosperm, or embryo, according 

 as those parts are present, and they are then termed the seed-coat 

 (episperni). Its cellular tissue gradually produces more or fewer 

 (one to five) layers of cells, developed in various ways. Frequently 

 the entire integument appears as a very thin membrane, especially 

 in one-sided, indehiscent fruits (as in the Grasses). We can usually 

 distinguish several layers. Nothing general can be stated respecting 

 the tracing back of these cellular layers to the integuments or thin 

 parts from which they originate; the history of development of 

 individual families, and even genera, must declare it for each 

 separately. 



In the perfecting of the seed-bud, new vascular bundles are 

 frequently produced in the parenchyma of the single or of the 

 outer integument, in connection with the termination of the vessels 

 of the funiculus, usually running out in elegant radiate forms from 

 it (as in the Hazel Nut, Lemon, &c.). The vascular bundle of the 

 raphe alone is often so prolonged, that it runs simple through the 

 entire circumference of the seed -bud until it reaches the micropyle 

 (as in many Composites). 



It often happens that individual parts of the integument become 

 more developed than the rest ; and here belong, in the first place, 

 those peculiar appendages of the raphe already spoken of, which 

 become still further developed ; or a new excrescence is now pro- 

 duced, usually only from a fold of the epidermis, which now 

 developes into two, rarely three usually vertical lines, into a mem- 

 branous border or wing all round the seed (a/a), or elevated ridges, 

 rising in various ways from the surface of the seed, and, if reticularly 

 connected, often forming little pits between them (as in Scrophula- 

 riacecs). Again, the exostome sometimes produces a peculiar ap- 

 pendage in the form of a papilla (Euphorbiacece), or a tuft of hair 

 (coma) grows out (as in AsdepiadacecR and others), or forms a cup- 

 like excavation with a fringed edge (as in Philadelphus), &c. In the 

 region of the chalaza, also, peculiar modifications of the cells are 

 often exhibited, appearing as papillae, gibbosities, and the like, or 

 as a variously, but often distinctly bounded colouring (as in Abrus 

 precatorius, Erythrina corallodendron, &c.).* 



* Link (Elcm. Phil. Bot. vol. ii. p. 285.) says, very inaccurately, the umbilicus in 

 Abrus precatorius is coloured black. On the umbilicus (hilum) the colour is not deep, 

 as that only occurs on the chalaza, and in Erythrina does not reach the umbilicus at all. 



