STRUCTURE.] ITS FORMS. 119 



B. Central hole small roundish. 



a. with distinct layers. 



3. Grains coarse, rough, and often stunted, in the pith of 

 Cycads. Some masses resemble the grains that are met 

 with in the scale-shaped subterranean leaves of Lathrsea 

 Squamaria. The inner layers form egg-shaped granules, 

 as in Potato starch ; the small exterior ones are compara- 

 tively irregular, being so excessively thick here and 

 there, that the whole grain is bluntly three-cornered. 



4. Grains egg-shaped. In the Potato. 



5. Grains mussel- shaped. In the Bulbs of the larger 

 Lily worts, as in Fritillaria, Lilium. 



6. Almost three-cornered in Tulips. 



b. With indistinct layers, or none. 



7. Grains blunt polygons in Zea mays. In albumen. 



8. Grains very small sharp-cornered polygons in Oryza 

 sativa. In albumen. 



C. Central hole long. 



9. Grains circular or oval, and in a dry state usually showing 

 a star-shaped slit. In Leguminous plants, for example 

 Pisum, Phaseolus. In seeds. 



D. Grains apparently cup-shaped, with a visible hole. 



10. Well marked in the rhizome of Iris florentina and in 

 allied species. 



II. Flat lenticular Grains. 



11. Layers evident or not, with a hole which may be in or 

 out of the centre, small and round or lengthened or 

 star-shaped and torn open. As in Triticum, Hordeum, 

 Secale. In albumen. 



III. Flat Plates. 



12. Layers visible, but it is at present doubtful whether 

 they are really included one within the other, or are 

 placed upon each other like watch-glasses. The first 

 appears probable, both from analogy and from the phe- 

 nomena observed in heating, and from dissolving in 



