(a) Simple or monarch starch-grains. Grains which have but one hilum.
(b) Complex starch-grains. Grains that axe formed from several starch-grains which are so crowded in one chromatophore that they become enveloped within common starchy layers, and thus bound into a single individual. Complex starch-grains may be diarch to poIyarch.
(c) Solitary starch-grains. Grains which grow singly in one chromatophore.
(d) Adelphous starch-grains. Those which grow along with other grains in one chromatophore. They may be di- to poly-adelphous; up to 6-adelphous would be designated as oligo-adelphous.
(e) Monotone starch-grains. Grains which during their entire life have undergone periods of solution, leaving coherent traces of each of the lamellae formed during the period of storage. Perfect monotone starch-grains in which there still exists a trace of every lamella which has been formed and in which, even if eccentric, the lamellae are closed are exceedingly rare. This term is also to be used in all cases in which no distinct characters of a polytone type are present.
(f) Polytone starch-grains. Grains that have during their development undergone two or more periods of solution in which numerous lamellae completely disappear or decrease in width, interspersed with other periods during which they developed as the relative monotone type. Polytone grains if they have an eccentric structure show a series of lamella) which are open laterally.
Meyer's 1895 Classification
A. Monarch Starch-Grains.
(a) Solitary Starch-grains.
I. Centric starch-grains. Hilum. in the mathematical center; lamellae always equal at two diametrically opposite points (Nägeli, Type 1).
(1) Monarch solitary, spherical. (Nägeli, Type 1.) Hilum spherical in the center of the spherical grain; lamellae of uniform thickness, forming complete circles.
(2) Monarch solitary, centric, lens-shaped. Hilum and grains rounded and compressed (also rounded-reniform. or rounded-oval, compressed).
(3) Monarch solitary, centric, oval grains. Hilum and grains oval and lanceolate-oval; circular in cross-section; lamella) equal at two diametrically opposite points, being coarsest at two poles.
(4) Monarch solitary, centric, rod-shaped, and cone-shaped grains are bone-shaped and somewhat flattened.
II. Eccentric starch-grains.
(5) Monarch solitary, eccentric, rod-shaped. Lamellae on one side the heaviest, and at the diametrically opposite side the finest. Grains are circular in transverse section; both ends of almost equal width and thickness.
(6) Monarch solitary, eccentric, conical. Lamellae are the densest at one side and the most delicate at the diametrically opposite side. Grains are conical; circular in transverse sections. Hilum located at the narrower, less dense end.
(7) Monarch solitary, eccentric, inverted-conical. Grains similar to those in Type 6, but with the hilum. at the more dense end. Grains of Type 7 are usually found in company with those of Types 5 and 6.
(8) Monarch solitary, eccentric, flattened.
(b) Adelphous starch-grains.
I. Oligoadelphous Starch-grains. If several starch-grains grow simultaneously in a chromatophore, they behave just as spherocrystals do when growing in an inexhaustible mother liquor. Only in the very earliest stage are the two starch-grains spherical, and, as is apparent, the spherical shape is the more pronounced the larger the chloroplast when the first grains start to form. If the chloroplast is still small when the starch-gains begin to grow, so that the grains develop along with the chloroplast and exceed it in growth, they are very soon prevented from increasing in size on the inner side, and both become flattened. The lamellae are heaviest within and below, and in purely monotone grains they are always closed, since the crystallization substance between the grains is furnished in the greatest quantity. Flattening of the grains results, as is readily seen if one considers that when two spherical grains grow side by side in a chromatophore, the chromatophore layer being thinnest where the two spheres come in closest contact with their surfaces. The entire process of growth of the diadelphous starch-grains is similar to that of monarch, solitary grains of Pellionia.
II. Polyadelphous starch-grains. The polyadelphous starch-grains of a chromatophore, which are not easily distinguished from the diadelphous, forms, are approximately similar in form and size, though the proportion of the diameter of the smallest to that of the largest is usually as 1 to 4. The greatest diameter of a chromatophore filled with starch-grains which was measured by Nägeli is 106 mu. Such a chromatophore may, according to Nägeli, contain between 10 and 30,000 growing starch-grains. The form of the polyadelphous grains is mostly polyangular or rounded with centric structure. Some exceptions are found in the flattened forms of Arenaria and A. graminifolia and Drymaria cordata described by Nägeli. The polyadelphous grains are found relatively seldom in rhizomes and roots, although there axe some exceptions, but occur most abundantly in the reserved food of seeds.
B. Complex (Di- to Poly-arch) Starch-Grains. It can not be readily demonstrated that complex grains, like certain grains, for example, of Pellionia, are descended from adelphous grains. It has, however, proven that all plant parts in which complex grains are present also at times develop adelphous starch-grains which correspond entirely with the central lamellie of the complex grains. Furthermore, gradations between the adelphous and the similar complex forms can be found. Additional proof of the connection between adelphous and complex starch-grains is the fact that plant parts which produce few and irregular adelphous grains likewise have relatively few and irregular complex grains in their cells.
