16 



The Florists' Review 



Febboabt 24, 1916. 



in the last year a number of states have 

 passed quarantine laws. These acts, 

 while seemingly a hardship on men im- 

 porting and making interstate ship- 

 ments of floricultural plants, will pre- 

 vent the introduction of any new dis- 

 eases. Although the federal act has 

 been established only a short time, al- 

 ready the inspectors have discovered 

 several serious diseases, which under 

 this act have been kept out of the coun- 

 try, by means of a strict embargo on 

 the plants on which the disease has 

 been found. Thus you have been saved 

 the possibility of having to combat a 

 few added diseases which might be- 

 come serious. 



You will find it a much more difficult 

 task to cure a plant already diseased 

 than to prevent the disease. In only a 

 few cases can you actually kill an or- 

 ganism which is already causing in- 

 jury. Only with mildews, as the 

 mildews on roses, where the fungus is 

 purely superficial, is the use of fungi- 

 cides beneficial. 



Disease-Besistant Plants. 



We now come to the third and prob- 

 ably the most important method of dis- 

 ease control; that is, the use of dis- 

 ease-resistant plants. Although the 

 importance of this method has been 

 well understood by scientists, the ap- 

 plication of the principle by breeders 

 of floricultural plants has not been 

 taken up to any extent. 



The breeder can undertake this phase 

 of the work from two standpoints: 

 First, the breeding of disease-resistant 

 plants, and second, the selection of re- 

 sistant plants of susceptible varieties. 

 The principles involved are similar in 

 the two cases. 



Before a disease-resistant race can be 

 bred, you must find individual plants 

 resistant to disease. It is a well known 

 fact that species in the same genus 

 exhibit marked differences in resistance 

 to disease. Select and use for breed- 

 ing purposes the species which appear 

 to be resistant, as well as any of the 

 wild species of floricultural plants, 

 which are resistant in many cases, even 

 though they are much inferior to the 

 highly developed cultivated varieties. 

 Cross these inferior but resistant va- 

 rieties with the more susceptible varie- 

 ties and you will develop a productive 

 as well as a resistant race. Even as 

 species in the same genus vary as re- 

 gards disease-resistance, so also varie- 

 ties and races of the same species vary. 



Immunity from disease of a resistant 

 plant, as a rule, is not permanent. This 

 is especially true where the vegetative 

 parts are used to propagate the plant 

 from season to season. It is, therefore, 

 of importance to the breeder to carry 

 on his work of selection and breeding 

 indefinitely. 



Conquest of Carnation Bust. 



Among the breeders of floricultural 

 plants the selection of resistant indi- 

 viduals has been carried out to some 

 extent. A number of years ago a car- 

 nation rust spread over the whole coun- 

 try in a short time and caused a serious 

 loss. The carnation breeders, after a 

 time, began to discard seedlings which 

 were susceptible to rust and used only 

 the more resistant varieties for cross- 

 ing. As a result, we find the carna- 

 tion varieties offered on the market to- 

 day to be highly resistant to rust, and 

 growers now pay little attention to 



this once serious disease. What is true 

 of carnation rust is also true of chrys- 

 anthemum rust. By discarding suscep- 

 tible varieties and crossing the more 

 resistant ones, the chrysanthemum rust 

 has practically disappeared in this 

 country. 



There is still an unlimited amount 

 of work to be done in this direction 



Dry Heat Soil Sterilizer. 



by breeders of floricultural plants. 

 Your carnation breeder, for example, 

 should produce a variety of carnations 

 for the south that will be resistant to 

 stem-rot and eelworms. At the present 

 time, growers in certain localities of 

 the south are finding it almost impossi- 

 ble to grow carnations, due to the rav- 

 ages of these two diseases. The solu- 

 tion of the problem of yellows, which 

 is general throughout the country and 

 increasing in seriopsness from year to 



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Transverse Section of Sterilizer. 



year, also must be solved by the car- 

 nation breeder. . 



Your aster specialist, in his breeding 

 work, should give you varieties re- 

 sistant to wilt, a disease which causes, 

 under certain conditions, a serious loss 

 in the field every season. So, also, your 

 violet specialist should develop varie- 

 ties resistant to root-rot, a disease 

 which has discouraged so many of you. 



The production of varieties resistant 

 to these diseases should go hand in 



Cross Section of Sterilizer. 



hand with breeding for color, size of 

 flower, and other points. 



Cause of Disease-resistance. 



The question might now be rightly 

 asked bv my readers: "What is the 

 cause or disease-resistance in plants?" 

 Immunity may be influenced by me- 

 chanical means of protection, rapid 

 growth and the chemical make-up of 

 the plant. Immunity may depend on 

 the character of the plant, on the thick- 

 ness of the wax layer, cuticle, cork or 

 bark, or on the number, arrangement 

 and location on the leaf or stem of 

 hairs, stomates and lenticels. 



For example, the wax layer, hairs. 



etc., on the leaf may influence the ra- 

 pidity of drying after watering. We 

 have found in some of our work here 

 that the quick-drying varieties were 

 less susceptible to a certain disease 

 than the slow-drying varieties. 



In the case of the carnation plant, 

 the breathing pores on the leaves close 

 quickly and tightly, thus keeping out 

 rust infection. It has also been found 

 that in some carnation varieties, even 

 though the fungus enters the breathing 

 pores, it is unable to penetrate farther. 



Not only is the thickness of the 

 cork necessary, but the rapidity with 

 which cork is formed. 



In some cases the plants grow so 

 rapidly that they outgrow the effects 

 of the fungus. However, in other 

 plants the reverse is true, in that 

 stunted plants may be more resistant 

 to disease than the more rapid-growing 

 plants. 



Of the influence of chemical sub- 

 stances in plants on immunity, little is 

 known. It has been shown, in some 

 cases, that disease-resistance may be in- 

 fluenced by the acidity of the cell sap, 

 the amount of sugars present in the 

 plant, and the production by the plants 

 of toxic-like compounds. 



George L. Peltier. 



WHAT DO YOU KNOW? 



A subscriber asks for the history of 

 the S. A. Nutt geranium, which ap- 

 pears to be lost in the mists of an- 

 tiquity. The Eeview will be pleased to 

 publish the story if some reader who 

 knows it will be so kind as to put it on 

 paper. 



STEBILIZATION BY DBY HEAT. 



Dry Heat Cheaper Than Steam. 



There have been frequent inquiries 

 from small growers for a more econom- 

 ical method of sterilizing soil than the 

 ordinary steam process. While the 

 original method of diffusing live steam 

 under the soil by means of perforated 

 pipes is an excellent thing, it is not 

 practical where the quantity of soil to 

 be sterilized is not sufficient to warrant 

 the investment in the necessary ap- 

 paratus. Inasmuch as the principle of 

 soil sterilization is simply to heat the 

 soil to a temperature that will ex- 

 terminate insects, fungi, spores, etc., it 

 is immaterial what form of heat is used. 

 Sterilization by dry heat has been tried 

 and found more adaptable to the need 

 of the small grower who has limited 

 quantities of soil to be treated. The ac- 

 companying illustrations and descriptive 

 matter on the dry heat sterilizer ap- 

 peared in a recent issue of the Garden- 

 ers' Chronicle, English. 



Figures and Facts. 



The perspective view shows a dry 

 heat sterilizer suitable for the purpose. 

 It is constructed of bricks and will con- 

 sume any kind of fuel. The floor on 

 which the soil is placed is between the 

 stove at one end and the chimney at 

 the other. Under the floor are four 

 parallel flues that radiate the necessary 

 heat. The length of the outflt may 

 vary, according to requirements, up to 

 fifteen feet. The width is four feet six 

 inches. The stove, or furnace, is two 

 feet six inches by three inches, and the 

 furnace entrance is eighteen inches 

 wide. The fireplace is the same width, 

 though it may be wider where it is in- 

 tended to burn refuse. The connection 



