Tlie Roots of the Wheat Plant. 177 



This table demonstrates what I have found in my own experi- 

 ments in wheat planting — that from 1 to 2 inches is the best 

 depth ; beyond this the plant becomes liable to joint-rooting, and 

 besides losing much time in coming up they become thin and 

 attenuated and do not stool or tiller, or if so this process is weak 

 and irregular, inasmuch as the lateral buds proceed from the 

 axils of the leaves, as in diagram 2 a a ; and if one bud succeed 

 another from below upv/ards, decay of some buds and irregularity 

 in the growth of others is the result ; if only the upper bud suc- 

 ceeds, which is the general case, much time is lost in the rectifi- 

 cation of the plant by the decay of its lower parts. 



b. The seed having been sown as evenly as possible at the 

 required depth the following changes take place. The grain 

 begins to obtain moisture from the soil, and consequently en- 

 larges in size : in a few days the embryo shows a great change, 

 in that it has become enlarged both above and below, the lower 

 part soon protruding as a rootlet, the upper as a bud, quickly to 

 develope leaves. Coincident with this proceed the chemical 

 changes in the cotyledon, from which the germ is supplied with 

 its food until the roots on the one hand, and the leaves on the 

 other, become capable of acting, the one as purveyors, and the 

 other as eliminators of that food with which the plant may be 

 surrounded in the soil and the atmosphere, and upon which 

 depends its after welfare. 



If wholesome plant- food be in the soil, it progresses favour- 

 ably ; if the reverse, disease or death will be the result. If the 

 supply of these be insufficient, the produce is small ; if too 

 great, we get blighted leaves and straw, with too sm.all a pro- 

 portional of corn. If bad seed be sown, we have a diseased and 

 malformed plant, resulting in thin, diseased, and consequently 

 blighted grain. All this, however, depends upon the air the 

 plants get to breathe ; if full of noxious vapours, they die ; a 

 small quantity of such gases as sulphuretted hydrogen, sulphurous 

 acid gas, and muriatic acid gas, acting as a poison, and thus 

 preventing wheat from being grown in the neighbourhood of 

 some chemical and manufacturing works. 



c. We now enter upon a more minute description of the sub- 

 sequent changes that take place in the growth of wheat roots. 

 After the radicle a, diagram 3, has burst through the in- 

 tegument lateral rootlets begin to develope themselves to its 

 right and left, which, in their young state, are but sheaths from 

 which protrude tlie true roots Z», this method of growth being 

 distinguished by the botanist as endorrhizal, from the Greek 

 word Evoov, witlnn, and is a characteristic of endogenous plants, 

 especially of the grasses. These roots elongate for a greater 

 or less length without branching, when slight projections mani- 



VOL. XVII. X 



