CHIEF FORMS AND CLASSIFICATIONS OF STARCH-GRAINS. 69 



A. Monarch Starch-Grains. — Continued. 



(1) Monarch solitary, spherical. (Niigeli, Type 1.) Hilum spherical in the center of 



the spherical grain; laniellse of uniform thickness, forming complete circles. 

 Examples of such grains are found in Sorghum vuhjare and in Zca mays. In the 

 latter, when the grains have reached two-thirds of their growth, tliey are spherical 

 with centric lamelhe. Grains which have just been removed from immature 

 endosperm cells show the distinct striations of the lamella;; later, Ijy pressure 

 due to the growth of neighboring grains, the solitary grains become angular; the 

 lamellae of these angular grains are closed, but are finer at the flattened surfaces. 



(2) Monarch solitary, centric, lens-shaped. Hilum and grains rounded and compressed (also 



rounded-reniform or rounded-oval, compressed). (Nageli, Type 10.) Examples: 

 Starch-grains from the seeds of Triticum, Secale cereale, Hordeum vulgare. In the 

 chromatophores of the endosperm of Hordeum small grains form early, and by 

 the rapid growth of several grains in a relatively small chromatoiihore become 

 mutually flattened. During the development of the endosperm cells the growth 

 of the grain within the chramato])horc is hindered, partly due to new formations, 

 partly through the solution of small grains so that starch-grains of various shapes 

 arise, such as laterally flattened, crescent-shaped, bean-shajied, etc. 



(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. (Nageli, Type 3.) Examples: Many grains from 

 the cotyledons of Vicia faba and other Papilionaceas. The starch-grains in the 

 cotyledons of Cicer arietimmi are instances of this form of grain. All the chro- 

 matophores lie in the primordial utricle and usually contain 1 starch-grain, or 

 rarely 2, which are flattened upon the sides in contact. Most of the starch-grains 

 correspond in form to that of the chromatophores, which are disk-shaped, although 

 of different densities. From time to time energetic solution takes place as a 

 consequence of rapid growth, so that most of the grains are irregularly outlined 

 and tuberculated in the early stages; later, the irregularities Ijccome less jiro- 

 nounced because there is less active solution. The chromatophore surrounds 

 the starch-grain almost uniformly as a green layer, the surface of the grain be- 

 comes more and more smooth and increases relatively more in thickness than in 

 width and breadth, since by the deposition of lamellre of uniform thickness the 

 grain grows more rapidly in the thick diameter than in the longitudinal. In the 

 mature grain a feebly refractive diffuse hilum is observed, the lamella; are strongly 

 refractive, and the grains have become rounded and almost oval. 



(4) Monarch solitary, centric, rod-shaped, and cone-shaped grains. (Nageli, Types 4 and 5.) 



E.xamples: Starch-grains from the lactiferous vessels of the Euphorbiaccw. Ob- 

 servations upon Euphorbia myrsinites show that the young starch-grains from the 

 latex are rod-shaped; most of them are irregularly corroded and have a feeljly 

 refractive line in the axis, which probably may be due to active fermentation and 

 swelling. Very slightly corroded grains are also rod-shaped with bilateral eccen- 

 tric lamellae. Since the younger laraellie are laid down directly after the growth of 

 the latex vessels terminates, they will be the most dense and hence proljably 

 withstand solution better than those lying nearer the middle of the rod-sha]ied 

 grain, and thus the explanation of the origin of the thicker ends may be similar 

 to that observed in the case of Oxalis ortgicsi. The starch-grains from older in- 

 ternodes are bone-shaped and somewhat flattened. The investigation of chro- 

 matophores from material which had been carefully hardened and stained with 

 fuchsin showed the grain completely' enveloped in the suljstance of the chromato- 

 phore, which, however, was more markedly massed at the two ends of the grain. 

 II. Eccentric starch-grains. 



(5) Monarch solitary, eccentric, rod-shaped. Lamellae on one side the heaviest, and at 



the diametrically oi)posite side the finest. Grains are circular in transverse 

 section; Ijoth ends of almost equal width and thickness. (Nageli, Tyjie 9.) Ex- 

 amples: In Diejjcnbachia and Iris germaniea. In Dieffenbachia beautiful mono- 



