412 Farmer. — On the Morphology and 
gradually obliterated, and complete union takes place. In 
this way the ovules become entirely enclosed in the pulpy 
tissue, even long before the fruit is ripe, and it is impossible to 
distinguish that portion whose origin is carpellary from that 
which is derived from the placenta. The changes which take 
place in the outer cells of the pericarp, and which result in the 
formation of an epicarp, have already been adverted to, and 
need not be further described, as they are essentially similar 
to those occurring in Rtibus , except that here the epicarp is 
somewhat thicker, and separates with greater ease from the 
inner tissues. 
Whilst the changes above detailed are proceeding, modi- 
fication is going on in the outermost layer of the ovular 
integument, which results in the formation of a protective 
shell, which takes the place of the endocarp in other fruits. 
The thickening substance, which soon becomes strongly 
lignified, is deposited on the inner or central wall, and extends 
partially up the lateral or radial ones, but, as in many other 
cases, it is not complete, and hence a section of the young 
seed shows these walls as spike-like projections which ter- 
minate in thin membranes. The outer, or peripheral, wall is 
not thickened at all, but its more external layers undergo 
mucilaginous change (PL XXVI, Figs. 31, 32) at a very early 
period. This mucilage may perhaps be regarded as part of the 
pulp, as it fills the interspaces left between the ovules and the 
surrounding tissues as a somewhat viscous mass. It is of 
extremely common occurrence in fruits, and owes its origin 
to the most varied sources ; we have seen it in Hedera , and 
in Ribes it is also met with, being derived from the placental 
cells ; and besides these instances it occurs in a great number 
of fruits, as Linum (where it is produced from the seed- 
coat as in Solatium ), whose ovaries do not become pulpy 
at all. 
As the fruit ripens the green colour changes to the well- 
known bright red, so characteristic of the berries when mature ; 
the change is due to the appearance of a great number of 
orange-red chromoplastids, which are, in part at least, derived 
