Biology Pamphlets (Volume 895)

This historic book may have numerous typos, missing text, images, or index. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. 1907. Not illustrated. Excerpt: ... IV. EXPERIMENTS ON IRRITABILITY. 1. Responses To Light. Experiment 116.--To determine the formative influence of light. 1. Place some cuttings of Opuntia in sand in the dark-room and germinate some seeds of a monocot (corn) and of a dicot in garden soil in the dark room. 2. Make some similar cuttings of Opuntia but retain in sand in the light, and germinate a similar lot of seeds under normal conditions of illumination. 3. Keep both lots uniformly watered and record temperatures in dark-room and without, 4. After growth has begun or germination has taken place compare the form, size, and structure of the different organs. which develop in darkness, with those which develop in the light, and keep the specimens under observation until the effect of darkness has been definitely established. Fig. 19.--A, Cactus plant grown under normal conditions. B, Cactus plant grown in darkness. Experiment 117.--To determine the effect of light on the rate of growth in a seed plant. 1. Place a potato in conditions favorable for growth and expose to normal illumination. This may be done by putting a potato in soil in a flower pot and nearly covering it with soil or using damp sphagum moss in the place of soil. 2. Arrange a second specimen in a similar manner but place in the dark-room. 3. After growth has started select one or more shoots on each specimen and measure the amount of growth for definite intervals. Allow the specimens to grow for several weeks and measure the total length. Observe also the formative effect of light. Experiment 118.--To determine the effect of light on the rate of growth in fungi. 1. Put some well decomposed compost in each of two damp chambers, moisten well, and expose to uniform conditions except that one should be in darkness and the other ...