242 CHAPTER XIV 



place. Consequently, any factor limiting starch formation 

 naturally increases the percentage of protein found. Imma- 

 ture, and grain shrivelled through disease, e.g., rust, has a 

 higher percentage protein content. 



Probably the composition varies most with changes in 

 climate. It is a well-known fact that what may be classed as 

 a soft wheat in some parts of the world, when grown under 

 other conditions may be called hard wheat. Some varieties 

 in some localities will present an opaque appearance, in others 

 both opaque and translucent kernels will be found in the same 

 crop, while in another situation the kernels from the same 

 strain may be entirely translucent. 



PercivaP states : " The white opaque appearance of the 

 endosperm of mealy (soft) grains is due to the presence of 

 minute fissures, which develop between and within the cells 

 during the desiccation which occurs at the time of the ripen- 

 ing of the grain. 



On examination of carefully-prepared transverse sections 

 from grains, showing different degrees of mealiness, it is seen 

 that interstices have formed along the line of union of adja- 

 cent cells and around the starch grains within the latter, and 

 the contents of some of the cells have shrunk more or less away 

 from the surrounding cell wall ; these changes appear first 

 near the furrow (crease) and spread radially outwards across 

 the endorsperm towards the aleurone layer on the dorsal side, 

 especially in the basal half of the grain near the embryo. 



Minute in-egular cavities are also seen in the aleurone 

 cells. 



From investigations on mealy grains of barley, Brown 

 and Escombe concluded that the interstices are vacuous or 

 only partially filled with air. 



Such minute spaces are absent from flinty, hard, trans- 

 lucent endosperm, in which all the cells of the tissue are 

 completely filled with starch grains imbedded in a protoplasmic 

 matrix, the whole forming a dense coherent mass. 



The production of flinty or mealy grains is a hereditary 

 character of some particular races and forms of wheat, e.g., 

 the grains of T. dnruni are almost always flinty, while those 

 of T. vulgare are usually very mealy. 



Wheats grown on heavy soils have a tendency to produce 

 flint grains, while on light soils the texture of the grains is 

 of a more mealy character. Percival also claims that wheats 

 closely spaced have a higher proportion of mealy kernels than 



