CONTENTS. The illoq contents of the cell arc the nucleus and the cytoplasm, but beside. these variou. other thing, may be pres ent. such as phut ids, starch-grains, crystals. oil drops, sap. etc. P/aRtids are differentiated por that, of the cytoplasm. and it has been believed by many that they are permanent organs of the cell, passed on from one cell generation to an other, and it is undoubtedly true that they divide and may persist throughout the greater part of the life history of a plant ; but whether they are present in the initial cell of the plant or not is a serious question, and if not, it mu.t be admitted that they may be formed de nano front the cytoplasm. are called leucoplasts,' and colored Ones 'chromato phore,.' If a •hromatophore contains chloro phyll the green pigment 1 it is called a `chloro pla,t; hut if it contains any other coloring matter it is a 'ehromoplast! The function of the leucoplast is to produce starch, but if light con dition. are favorable the leucoplast may be con verted into a chluroplast. (.71doroplasts vary greatly in form, in size, and in the number found in a single cell. In the plant, they are small flattened or discoid bodies, and many arc usually found in a cell. However, in
Anthoceros (a liverwort) and Selaginella (little there is only one in a cell. The greatest variety of forms is found among the seaweeds (Alga.), where there are not only the small discoid forms, but also flattened plates, coiled bands, etc. The ehloroplasts, like the leu coplasts, produce starch, hut they are also able to manufacture carbohydrates in the presence of light (photosynthesis, q.v.). Starch-grains vary in form and size. While the size may vary greatly with age, the form is usually character i.tie of a given plant. The starch formed by the chloroplasts is in the form of very small gran ules, which do not become large grains, but dis appear when light is removed, and are probably carried to other portions of the plant. The ordinary starch-grain, are developed in the pro toplasm. Crystals composed of caleinin oxalate are widely distributed. In form they are pris matic, euldeal, oetohedral, a•ienlar. etc. Those which are needlelike in form are called `raphides.' ('ystolith, composed of calcium carbonate are ranch less common.