Text-book of structural and physiological botany . grains of the shape of a rod or bone are found in thelatex of tropical Euphorbias, &c. (Fig. 46.) Mature starch-grains consist, as a rule, of a num er of layers whichappear to have been deposited around a central or eccentric nucleus ;but it is impossible to believe that separate layers have been actuallyso formed in the course of growth; it is much more probable thatthey grow by intussusception (see p. 15), and that the stratification isonly the consequence of the layers or shells containing a larger orsmaller quantity of water, as is shown b
Text-book of structural and physiological botany . grains of the shape of a rod or bone are found in thelatex of tropical Euphorbias, &c. (Fig. 46.) Mature starch-grains consist, as a rule, of a num er of layers whichappear to have been deposited around a central or eccentric nucleus ;but it is impossible to believe that separate layers have been actuallyso formed in the course of growth; it is much more probable thatthey grow by intussusception (see p. 15), and that the stratification isonly the consequence of the layers or shells containing a larger orsmaller quantity of water, as is shown by perfectly dry grains of starchbeing unstratified throughout. Those grains which contain two or more ^ An exception is perhaps afforded by the membranes of the asci ofLichens, with respect to which, however, it is at present undeterminedwhether they contain starch or not. 28 Structural and Physiological Botany, nuclei, surrounded by a common system of peripheral layers, are termedsemi-compound (Fig. 42 d) ; compound when the divisions which.
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