The Weekly Florists' Review. 



423 



final stage of the disease when the cells 

 have broken down is shown by Fig. 7. 

 Compare with Fig. 3, which shows a sec- 

 tion of a healtliy leaf. H iii:>y lip that 

 something injecled with tlir _., I^t iiimis 

 material slowly dilTusos iIiimujIi ih, (ills 

 in the region of the puii.tmr, rj\isiiig 

 them to slowly die. 



One of the first things that may be 

 observed by a chemical study of the dis- 

 eased cells is a decrease of the nitro- 



tion of the plant starch is made in the 

 green cells during the day. It is later 

 converted into sugar by a chemical fer- 

 ment known as .diastase, and is then 

 used for food by the plant as a who!e, 

 being transported to all parts. This 

 change from starch to sugar is greatly 

 retarded when the chemical ferment that 

 causes c.xidation increases beyond the 

 normal amount. The food materials of 

 the diseased plants become very slug- 

 glish in their movement and are prob- 

 ably very easy for the insects to get. 

 The plant itself suffers from a sort of 

 indigestion, and soon loses in vigor, be- 

 coming much more susceptible to all un- 

 favorable conditions as well as to in- 

 sect and fungus parasites. Careful .ex- 

 amination has shown that when these 

 abnormal changes have been once 

 started in a plant the ill effects continue 

 long after the initial cause hag disap- 

 peared. 



If the insects are killed or kept off of 

 such a plant the new growth will be 

 free from spots and therefore apparently 



Fisr. 7. Till- hist slaso of tla-disL-usc. Tlie cells 

 ;irc? de;ia iiiul hiivi- collapsed. 



The Carnation in Health and Disease. 



healthy. It is, however, poor in reserve 

 albumin and has an excessive amount of 

 oxidizing enzymes, as explained above, 

 and is therefore in fact diseased. This 

 mal-nutrition becomes gradually cumu- 

 lative from generation to generation of 

 cuttings and so far as our investiga- 

 tions have gone cannot be cured. Stim- 

 ulating manures intensify the trouble in- 

 stead of correcting it. 



It was noted in these experiments, 

 and, indeed, it is a well known fact, that 

 certain individual plants of any given 

 variety are much more susceptible than 

 others to injury from these causes. In 

 fact, some plants hardly react at all to 

 aphis punctures, while" others become 

 badly diseased. The aphides do not 

 thrive on the resistant plants, but in- 

 crease rapidly on the plants that are 

 not resistant. This was found to be 



lion produced by excessivi 

 The Carnation 



food by aphides during g-rowth. 

 Health and Disease. 



due to the fact that the resistant plants 

 were rich in reserve nitrogen and did 

 not have an excessive amount of the 

 oxidizing ferment, and were also rich in 

 tannin, a substance which aphides great- 

 ly dislike. On the other hand, the plants 

 which the aphides thrived on were poor 

 in reserve nitrogen, poor in tannin, and 

 rich in the oxidizing ferment, while at 

 the same time they were of slower 

 growth, lighter colored, and the tis- 

 sues less slimy when crushed or broken 

 than the resistant plants. To get re- 

 sistant strains therefore it would be 

 necessary to propagate only from these 

 resistant plants. 



There is evidence also which indi- 

 cates strongly that this diseased condi- 

 tion of nutrition may be induced by un- 

 favorable conditions of growth. For 

 example, severe cutting back of the 

 plants during active growth makes the 

 new growth that develops very sensi- 

 tive to insect punctures. Severe in- 

 jury to the roots in transplanting dur- 

 ing active growth also makes the plants 

 very sensitive to disease. The tissues in 

 these cases show the same chemical re- 

 actions that I have before pointed out 

 for diseased plants. Rapid growth in- 

 duced by high moisture content of soil 

 and air produces tissues showing this 

 same sensitiveness to injury by insects 

 and richer in oxidizing ferment than 

 plants grown under more favorable con- 

 ditions. It is evident, therefore, that 

 unless careful selection is practiced va- 

 rieties which respond readily to these 

 unfavorable conditions would gradually 

 become so subject to disease as to make 

 them unprofitable. 



It is a peculiar fact that plants which 

 are most subject to insect injury are 

 also most subject to injury by parasitic 

 fungi and probably for the same reason. 

 Too much attention, therefore, cannot 

 be given to kr, pin- .-i>.]^ up to a high 

 standard of ii,inii:il \ u. l.y careful se- 

 lection of cullin-- ii( III \i-nrous plants 

 and by careful allnilinii in the general 

 needs of the plant. If this were done 

 the prevalence of disease of all kinds 

 would be reduced to a minimum. This, 



of course, is not a new proposition to 

 florists or to others who make a busi- 

 ness of growing and studying plants. 

 You know perhaps better than anybody 

 else that unless rigid selection is prac- 

 ticed stock will run out. In these in- 

 vestigations some ot the causes of de- 

 terioration and the nature of the changes 

 have been determined. 



In concluding this paper I will men- 

 tion briefly three diseases which have 

 been unusually prevalent this year. The 

 first of these is stem rot, which is being 

 investigated " by Messrs. Stewart and 

 Duggar. As a special time has been set 

 apart at this meeting for discussing this 

 disease I will not enter into it here. 



Probably the next most serious car- 

 nation disease this year has been the 

 leaf spot caused by the fungus Septoria 

 dianthi Desm. A diseased plant from 

 one of our own greenhouses is shown in 

 the illustration. Fig. 9. The spots are 

 usually more or less irregular in out- 

 line and bordered by a dark purple mar- 

 gin. . The spores form on the lighter 

 central area of the spot within little 

 black bodies barely visible to the naked 

 eye. . 



The fairy ring spot caused by the 

 fungus Heterosporhm cchinulatum 

 Berk, has been the cause of serious in- 

 jury in some eases this season. The 

 spots produced by this fungus are usu- 

 ally more regular in outline. Fig. 10, the 

 central area of the spot being covered 

 by a gray mold-like growth made up of 

 the spores of the fungus, leaving a nar- 

 row border of light brown dead tissue 

 from which the name fairy ring may 

 have arisen. 



This disease attacks not only the 

 leaves and stems, but also the flower 

 buds. Both of these diseases develop 

 most rapidly and do most serious dam- 

 age to plants that have been injured in 

 transplanting from the fields to the 

 houses. In many sections the dry, hot 

 weather that prevailed last fall during 

 the time the plants were being moved 

 in was very unfavorable. The root sys- 

 tems were 'injured in lifting the plants 

 from a dry soil and they adapted them- 



