BOTANICAL CHARACTERS 123 



93. The Endosperm. — This is the mass of tissue lying CHAP. 



below the aleurone layer, but above and partly surrounding 

 the embryo. It comprises about 73 per cent of the whole 

 grain. Its function is that of a reserve store of elaborated 

 plant-food for the use of the young seed-plant before it is able 

 to absorb food materials from the soil or to elaborate them in 

 the leaf. 



As seen in section, the endosperm shows a variation from 

 translucence to opaque snowy whiteness. Hopkins (3) reports 

 a difference of 2 per cent more protein in the corneous than in 

 the white endosperm ; Hunt (1) questions whether this may 

 not be due to lack of complete separation from the aleurone 

 layer in the samples analysed. The latter author points out 

 that there is no material difference in structure noticeable under 

 the microscope, which has led to the suggestion, not positively 

 proven, that the difference between them is a difference in 

 density analogous to the difference between snow and ice. 



The relative proportion and arrangement of the translucent 

 or corneous and the white endosperm have been used in part 

 to differentiate between the five varieties of maize. 



94. Form for Describing the Grain. — This may be used 

 to advantage for the same purposes, and in the same manner, 

 as the form for describing the ear. 



For the use of students in agricultural botany, twenty-five 

 to thirty grains should be given of each of the five varieties, or 

 of five breeds of one variety. For determining the points in 

 (I) to (/>) inclusive, a number of grains should be soaked in hot 

 water for thirty minutes, or in cold water for twenty-four hours. 

 For measuring the grains, a sheet of cross-ruled paper can be 

 used to advantage for marking off distances, which can then 

 be measured accurately by a scale divided to 32nds of an inch, 

 or preferably to millimetres. 



Name : Variety Breed 



Date of (a) record ; (A) sowing ; (c) harvest 



(a) Weight' ten average grains in duplicate (a) ; (ft) 



(6) Length: ten average grains in duplicate (a) ; (b) 



(c) Width: ten average grains in duplicate (a) ; (b) 



(d) Thickness : ten average grains in duplicate (a) ; (b) 



(<•) Ratio of width to length : divide length of ten grains by width of ten 



grains (a) ; (A) 



(/) Ratio of thickness to width: divide width of ten grains by thickness of 



ten grains (a) ; (ft) 



IV. 



