THE GRAIN OF WHEAT. GERMINATION. 421 



the place from which, in germination, the radicle will protrude, 

 it shows still further reduction and a depression (m) is visible. 

 The fruit has a very short stalk (p), and we can see the vascular 

 bundle (vp), which enters here and passes into the funicle of the 

 seed, which is fused, however, with the pericarp, and the vascular 

 bundle is hardly recognisable. Farther inwards, however, can be 

 seen a much more noticeable string of grey- brown elongated, 

 slightly-pitted cells, which we have already noticed in the cross- 

 section. The vascular bundle itself is embedded in delicate walled, 

 colourless, slightly-elongated cells. Farther inwards are the layers 

 of nucellar cells, with fairly thick, white walls, and then comes 

 the aleurone layer of the endosperm. This is readily separable 

 from the nucellar cells, so that an air-space is often present at this 

 part. Towards the embryo the endosperm is not bounded by an 

 aleurone layer, but by a fairly thick layer of swollen cell-walls, 

 which represent endosperm cells which have been crushed back 

 by the enlarging embryo. 



Germination of Wheat. The ripe grain of wheat germinates 

 very easily, and we will therefore make use of it in order to study 

 the early stages of germination. It will suffice to lay ripe grains 

 in moist sawdust ; it is even enough to stand ripe ears for a few 

 days with their lower ends in a glass of water. The pericarp 

 of the grain is first of all broken through at its weakest part (m), 

 that which corresponds with the micropyle of the seed ; the 

 coleorhiza is protruded, and out of its tip the rapidly-lengthening 

 radicle soon projects, the coleorhiza surrounding its base like a 

 sheath. Above this point the lowermost pair of lateral roots 

 subsequently arise, each likewise surrounded at its base by a 

 root-sheath, or coleorhiza. The whole grain swells considerably, 

 and ruptures the pericarpic covering more or less completely. If 

 this is lifted off, we can easily see, with the lens, the epiblast 

 between the bases of the two lateral roots. The cotyledonary 

 sheath elongates, and assumes a greenish colour. After it has 

 attained about fifty-fold its original length, it is broken through at 

 its apex by the first bright green foliage leaf. Considerably later 

 than the first, or lower, pair of lateral roots is produced a second, 

 upper pair. The original distance apart of the structures in the 

 neighbourhood of the lateral roots remain unchanged, and shows 

 that the hypocotyl undergoes no considerable elongation. The 

 lateral roots soon equal in development the principal roots, a tap- 

 root is therefore not produced. From a seedling which has already 



