52 MANUAL OF GENERAL AGRICULTURE. 



3. Oxygen Making. Place some green aquatic plant 

 in a glass jar full of water in front of a sunny window at 

 about 70 F. In a short time note the formation of oxy- 

 gen bubbles looking silvery by reflected light. Remove to 

 a dark place and after a few minutes examine by lamp 

 light to see whether the rise of the bubbles still continues. 



One of the most important facts about life is the 

 taking in by plants from the air of carbon dioxid, a com- 

 pound composed of carbon and oxygen. The plants use 

 the carbon and give off the oxygen. The process is the 

 opposite in the case of animals, which breathe off car- 

 bon dioxid and breathe in oxygen. Plants by a dusty 

 road side often become covered with dust. What effect 

 would this have on 1, 2 and 3? 



53. STUDY OF THE CHARACTERS OF BARLEY.* 



Materials for this exercise and also for exercises 54 

 and 55 may be obtained from the University of Nebraska, 

 Department of Field Crops, Lincoln, Neb. For Exercise 

 53, Order Lot 3. This lot contains nine barley types with 

 about 25 specimens per type. Price per lot $1.75. For 

 Exercise 54, Order Lot 58. This lot contains fourteen spe- 

 cies of cultivated grasses given in the exercise, together 

 with one additional. Price per lot $1.75. For Exercise 55 

 (a) Order Lot 59. This lot contains the seeds of eleven 

 species of clovers given in the exercise with two addi- 

 tional. Price per lot in 2-ounce bottles $1.50. For 55 (b) 

 Order Lot 58, which contains the seeds of the fourteen spe- 

 cies of cultivated grasses given in the exercise with one 

 additional. Price per lot in 2-ounce bottles $1.25. One or 

 more lots may be ordered, but the lots will not be broken. 



Cultivated barleys include a number of types, or 

 races, and may be classified as follows: 



(1) Two-rowed barley Hordeum sativum distichon 



(2) Six-rowed barley Hordeum sativum hexastichon 



* The two-rowed barleys commonly grown are charac- 

 terized by their large, plump grain. In Europe these bar- 



*For exercises similar to this on corn, wheat and oats see 

 ' ' Examining and Grading Grains ' ' by Lyon and Montgomery. 



