Rural School Leaflet 1049 



grow and form new yeast-plants. If you could look for some time through 

 a microscope at some healthy, growing yeast-plants, you would see a very 

 interesting process. Tiny round buds would appear on the sides of some 

 of the plants, and after a while these would become as large as the parent 

 and send out buds of their own, until finally, if the conditions were right, 

 there would be a little colony of many plants. 



Although you cannot see these tiny living things without the aid of 

 a good microscope, you do not have to depend on seeing them in order 

 to know that they are there and to learn many things about them. It is 

 easy to plant a yeast garden and to raise a good crop quickly if you supply 

 the right conditions, for healthy, vigorous yeast-plants grow rapidly, 

 and you soon know that they are at work because of the changes that take 

 place in the field in which you have planted them. Wherever they feed 

 they produce a change known as fermentation, and you are familiar 

 with this in rising bread-dough and in spoiling fruit. 



If you are to be successful in raising good yeast you must know how 

 to feed it and to care for it, because, like any other crop, it needs looking 

 after. Food, air, moisture, and warmth are all necessary for the growth 

 of yeast, and if it is to thrive well it should be planted in a well-weeded 

 garden. 



Originally all yeast was wild, but that used by man to-day is carefully 

 cultivated by persons who make it a special business to grow these little 

 plants and put them up in a convenient form for sale. Wild yeasts are 

 very abundant and flourish particularly on fruits, about fruit trees, vines, 

 and bushes, or wherever there is any sweet solution to feed on. The 

 foods best liked by yeast are those containing some form of sugar, as 

 fruit juices, molasses, and dilute sugar solutions; and yeast grows well 

 in a mixture of flour and water, for the dough contains enough sugar to 

 satisfy the yeast-plant. In feeding on sugar, yeast converts it into 

 alcohol and a gas known as carbon dioxid. This gas causes spoiling 

 fruit to bubble, but it is useful in bread -making for it gets caught in the 

 meshes of the dough and stretches it, causing it to rise. If the crop of 

 yeast-plants in bread-dough is good and vigorous, there is a large yield 

 of carbon dioxid and the bread rises well and is light. 



Yeast cannot stand much heat, and if it is sown in a field of very hot 

 liquid it is quickly killed. This is particularly true of the cultivated 

 yeasts used in bread-making, for the wild yeasts are likely to be more 

 hardy. If we are canning fruits it is very desirable to boil them so as 

 to destroy any wild yeast that may be present, for in that case the yeast 

 is a weed because it is growing where it is not wanted. In making bread, 

 however, we must be careful not to have the liquid hot, since it is our 

 desire to make the yeast grow. The temperature most favorable to the 



