530 



The Weekly Florists^ Review* 



Jandabt 26. 1905. 



understood that I mil not take up the 

 time to dpeak of them. The others are 

 not 80 well understood. 



Physiological Diseases. 



Physiological diseases result from the 

 disturbances of the functions of a plant 

 from any cause whatever. Less tha,li 

 three-quarters of a century ago it was 

 the common view that all cultivated 

 plants must be regarded as diseased be- 

 cause they were growing under unnatural 

 conditions. Therefore, it was reasoned, 

 their functions must be disturbed. We 

 no longer follow this mode of thinking. 

 There is no reason to believe that plants 

 are weakened or impaired in vitality by 

 continued cultivation. It is true that we 

 cannot define what we mean by "vital- 

 ity" in a plant, but if its vitality was 

 impaired by continuous cultivation we 

 should finally expect it to die. This has 

 not been our experience. Wheat has been 

 in cultivation for thousands of years and 

 the plants are more vigorous and give 

 greater yields today than one thousand 

 years ago. You will perhaps mention the 

 "running out" of varieties. I do not 

 think varieties have run out. They have 

 been superseded by better ones and by 

 comparison the older variety has appeared 

 to run out. We have no record but our 

 judgment to show that any variety has 

 run out. It is true, certainly, that all 

 plants vary under cultivation, and the 

 same seed pod may give some offsprings 

 of a weak and some of a vigorous habit, 

 but this is incident to cultivation and not 

 caused thereby. The cause lies in the 

 unknown factors governing the variation 

 of plants. 



As physiological troubles we mention 

 the "sleeping" of flowers and bursting 

 of the calyx. The cause of those trou- 

 bles rests to a great extent in the nature 

 of the variety, but to some extent also 

 in outer conditions. The very fact that 

 the calyx of certain varieties bursts with 

 some growers, but not with others, shows 

 that this trouble is greatly influenced by 

 outer conditions and can be solved by 

 experimentation. As yet, as I have said, 

 these subjects have never been scien- 

 tifically investigated. It is to be hoped 

 that some time these questions will re- 

 ceive their proper share of attention by 

 our experiment stations. 



Fungous Diseases.*?! | — »;1V< 



In considering fungous diseases we 



must keep in mind distinctly one thing: 

 These diseases are caused by distinct 

 parasitic organisms. A fungus is an in- 

 dividual organism just as much as the 

 carnation plant is. It has a vegetative 

 period and finally producesjspores, which 

 again reproduce the same fungus. Its 

 whole development can be followed with 

 the same certainty with which the de- 

 velopment of any plant can be followed 

 from seed to maturity. Parasitic fungi 

 live in the tissues of other plants, spread- 

 ing in the same manner as roots in the 

 soil. In this way fungi produce diseases 

 by destroying the tissues of the plants 

 upon which they feed. 



Diseases of this nature are often at- 

 tributed to some sort of unfavorable con- 

 ditions, such as lack of ventilation, too 

 much water, deep planting and the like. 

 This is an error. While certain condi- 

 tions favor the growth of fungi, and thus 

 cause disease to appear more abundantly, 

 it is nevertheless true that such diseases 

 would not appear if the fungi were ab- 

 sent. The fungi are in every instance 

 the prime cause of disease, not the condi- 

 tions. 



There are at the present time but two 

 fungous diseases of the carnation which 

 we need to discuss, the rust and stem-rot. 

 The rust was a prevalent disease about 

 ten years ago. At that time it was feared 

 as the worst enemy of the carnation, as 

 its frequent discussion in the horticultural 

 literature of that time indicates. It still 

 appears spasmodically here and there on 

 some varieties, but it is no longer the 

 dreaded enemy of the carnation. We 

 will come back to the causes of this 

 again. 



The Problem of Stem-Rot. 



The stem-rot is a far more serious dis- 

 ease and one which will be difficult to 

 control. It is caused by a fungus of the 

 genus fusarium. While the name of the 

 fungus may not carry with it any special 

 significance, we shall see presently that 

 this is one of a great group of fungi 

 which have received considerable atten- 

 tion of late, and that the study of this 

 group has been the chief means of de- 

 veloping a new method for controlling 

 diseases. These fungi are the causes of 

 the now well known "wilt diseases" of 

 many plants. The wilt diseases of the 

 cotton, cowpea, watermelon, flax and 

 aster are caused by species of fusarium. 

 These diseases have been carefully in- 



vestigated and from the knowledge gained 

 from them we can fill out, tentatively at 

 least, such points as are stiU unknown 

 m the life of the carnation fusarium. 



Stem-rot is not primarily a rotting of 

 the stem, but a wilt disease first mani- 

 festing itself by a wilting of the leaves 

 of some shoots. Very often only th» 

 leaves on one side of a shoot wilt and in 

 nearly all cases only a part of the plant 

 is affected. This is more especially true 

 during the early stages of the disease. It 

 will frequently be found that the 

 branches on one side of the plant are 

 affected and sometimes only those arising "^ 

 low down on the main stem. The disease 

 always progresses upward. The leaves on 

 the affected branches soon die and turn 

 to a pale color without dropping. The 

 upper leaves on these branches may be 

 wilted but still grow, until the whole 

 branch finally dies. The calyx lobes or 

 flower stems usually turn yellow at the 

 tips before the upper leaves begin to die. 



The root systems of these plants ap- 

 pear healthy externally with the excep- 

 tion of one or two roots. These are com- 

 pletely decayed so that only a remnant of 

 them is left. Yet if the diseased plants 

 are carefully examined after the roots 

 have been washed these decayed roots 

 can always be found. Here is evidence 

 that the fungus has entered the plant 

 from the soil through the roots. 



The course of the fungus in the plant 

 and the reason for the peculiar damage 

 it causes can be easily seen by cutting 

 microscopical sections at different parts 

 in the diseased stem and branches. The 

 fungus grows from the infected roots 

 into the water-conducting channels of the 

 stem and branches. When the disease is 

 severe these can be seen to be literally 

 plugged up with a mass of the mycelium 

 of the fungus. It is then impossible for 

 the plant to obtain sufScient water and 

 wilting and death are the results. Some- 

 times the fungus invades only the ducts 

 on one side of the stem and then the 

 leaves and branches on this side wilt. 

 Later when the plant is dying the other 

 tissues are also invaded, first the pith and 

 then the cortex. The fungus produces 

 innumerable spores on the dead stems and 

 on the lower portions of the leaves. 



The Cause and the Remedy* 



So much for the effect of the fungus 

 on the carnation plant. Questions of 



The Qoss for 100 Blooms Lowson Shade of Pink ot the Chicago Exhibition. 



fThe exhibitors and varletieB are, from left to rlirbt: Dorner, Eclipse; Pohlmann Bros. Co . H. W. Buckbee. W. J & M. S. Vesey, Breitmeyer's Sons, 

 Emll Buettner, each with LawBon: Thompson Carnation Co., Nelson Fisher; Chicago Carnation Co., Lawson.) 



