(b) The growth of the radicle.—Day by day the radicle becomes longer. Is it all growing longer, or does the increase in length take place more at one part than another? To answer this question, take five or six inches of cotton thread and moisten the middle part with Indian ink. Lay the seed on a flat ruler, so that the radicle lies over an inch divided into—say—tenths. Hold the thread tight, and press the inked part gently on the radicle, making about five marks at equal intervals from the point upwards. The ink will dry almost immediately. Then carefully replant the seed, taking care not to injure the radicle. After a few days take it out again, lay it once more on the ruler, and measure the distance between the marks. The radicle is evidently the young root. (c) The root-cap.—Hold up the radicle to the light, and examine its tip with a lens. Try to see that the tip is covered by a little cap, somewhat like a very small thimble. This is called the root-cap. (d) The root-hairs.—Hold a seed, with the radicle about an inch long, against a dark surface. Is the surface of the radicle smooth, or can you see any fluffiness on it? Is all the radicle fluffy, or only a part? Which part? As you examine older and older seedlings notice how much of the radicle is fluffy, and where the fluffy part is. The fluffy appearance is caused by fine, closely-set hairs, called root-hairs. (e) The plumule.—How soon after planting does the plumule become free? Does it grow upwards or downwards? The plumule is evidently the young stem. [Pg 11] As soon as the young stem is old enough mark it with Indian ink as you marked the young root, and replant it to find if there is any difference in the rates of growth of its different parts. (f) The fate of the cotyledons.—From time to time examine the cotyledons and notice that as the seedling grows larger they become more and more shrunken. Something is evidently being taken from them, perhaps to feed the young plant. We shall inquire into this by further experiment (Chapter II.). Do the cotyledons remain in their original position, or are they carried upwards with the growing stem or downwards with the growing root? 2. The yellow lupine.—In the same way observe how this seed grows. Do the cotyledons shift their position or change in colour? Do they become leaf-like? How do they differ from later-formed leaves? What becomes of them at last? What becomes of the seed-coat?