246 PART III. VEGETABLE PHYSIOLOGY. 



stages of germination, while no evidence of it will be seen in the Indian corn 

 and pumpkin seeds. 



Renew the experiment as regards the latter two, planting the pots with fresh 

 seeds, Lest the others may have been injured in the previous experiment, this 

 time subjecting them for the same period to a constant temperature of about 

 6o° F. If the seeds are good, both kinds will now germinate. 



Vary the experiment by planting the pots anew with the same seeds as at 

 first, but now subject them to a temperature of about 85 F., and after a few 

 days examine. The seeds will be found to have germinated much more rapidly, 

 and at the end of a week's time to have made a much greater growth than in 

 either of the previous experiments. 



When the plants have attained a height of two or three inches above the 

 soil, try the following experiment : Place the pot containing the barley plants 

 in a tin pail, and sink the latter nearly to its brim in a larger vessel containing 

 water ; now, after loosely covering the vessel and inserting a thermometer bulb, 

 heat the water very gradually, so that the temperature of the pot and its 

 contained earth and plants will rise pari passu. When the temperature of the 

 water has reached 122 F., remove the source of heat and let the water slowly 

 cool to the normal temperature of the room. Repeat the experiment with each 

 of the other seedlings, and after the plants have stood exposed to the air a few 

 hours, note the results in each case. 



4. Remove a few leaves from a Begonia, Pelargonium or any common 

 plant, weigh them accurately, and then place them in a clean capsule and heat 

 them for a considerable time to a temperature not exceeding 21 2 F. That 

 this temperature may not be exceeded, the heating had better be done over a 

 water bath. When thoroughly dried, again weigh them, and the difference 

 between this and their former weight will represent the proportion of free water 

 that existed in their tissues. Calculate the per centage of dry solid matter and 

 of water. 



Now enclose the dried leaves in an iron tube, such as a piece of gas-pipe, 

 and having sealed up both ends with fire clay, subject the tube to a red heat 

 for some time. After the tube has been thoroughly cooled, unstop the ends 

 and carefully remove the leaves. They will be found to be carbonized, but their 

 original form will be retained, even the finer veins and stomata being percepti- 

 ble under a magnifying glass. Weigh them, and the weight represents the 

 mineral constituents, or ash plus a much larger proportion of carbon. A part 

 of the carbon has been driven off by heat in the form of volatile compounds. 

 With care the remaining carbon may now be burned out by heating the leaves 

 to redness for sometime in an open tube, but care must be taken lest the ashes 

 be blown away in currents of air and lost. When the process is completed, 

 weigh the ash and calculate its percentage. 



5. Cut oft two branches of the House Geranium (Pelargonium zonale) 

 selecting those of nearly equal size and age, and subject them to cold a few 

 degrees below the freezing-point, until the tissues are frozen. Remove one to 

 a warm room and let it thaw rapidly. Submerge the other in a considerable 

 quantity of ice-cold water, and let the containing vessel stand in a moderately 

 warm room until it has acquired the temperature of the room. The immersed 



