PROTECTION OF GARDENS FROM FROST. 89 



fruit. With flowers and garden truck this can be much more easily 

 accomplished than with fruit. 



In this respect the gardener has a decided advantage over the 

 orchardist. The following is an excellent statement of how the plant is 

 injured : 



HOW LOW TEMPERATURE INJURES PLANTS. 



"Low temperature congeals the watery part of the cell sap, and also 

 the intercellar water content of the plant ; , within certain limits this 

 is not or may not be injurious, providing the protoplastic contents of 

 the cell are able to reabsorb the water and do this before the cell 

 structure collapses, as a result of insufficient cell turgor. Frequently 

 the frosting of plants is followed by a sudden raising of temperature, 

 in which case much of the water which was part of the cell sap in the 

 normal condition of the plant escapes through the cell wall into inter- 

 cellular spaces or even from the plant entirely, and thus the proto- 

 plasm of the cell, being unable to assume its normal condition, becomes 

 disorganized, and decomposition follows." Professor E. R. Lake, in the 

 Oregon Climate and Crop, July, 1900. 



PROTECTIVE MEASURES. 



From what precedes it is evident that our protective methods are 

 of two kinds, one intended to prevent the fall in temperature to the 

 critical point, and the other intended to prevent a too sudden warm- 

 ing of the chilled plant. 



Under the first class the most effective method is that of the wire 

 baskets. The cost of the wire basket is about ten cents, the cost of the 

 fuel per night can hardly exceed twenty-five cents, and to these add the 

 cost of labor in refilling the baskets on the succeeding day. One such 

 basket should protect an area of about six hundred square feet. Experi- 

 ments in the orange groves have shown that with twenty-five or thirty 

 of these baskets to the acre, the temperature has been raised four or five 

 degrees. There are other methods of warming the air, but this is prob- 

 ably the cleanest and most satisfactory. Oil pots are apt to leave a 

 deposit of soot which may be objectionable. Opposed to the methods 

 of direct warming or heating are methods based upon screening OP 

 covering. The purpose here is to prevent the fall in temperature by 

 choking off radiation. In other words, as with a hothouse, we aim to 

 entrap the earth's heat, and prevent its dissipation into space. It 

 would seem theoretically that this method might be used with great suc- 

 cess in the protection of gardens, because the construction of a screen 

 three or four feet above the ground is a less difficult matter than the 

 erection of such a screen sufficiently high to cover fruit. These screens 



