January 29, 1890.] 



Garden and Forest. 



59 



the house suddenly. (5) Humidity of atmosphere. (6) 

 Adaptation of methods to change of habits in plants. Plants 

 rarely, if ever, maintain the same habit of growth when forced 

 as they naturally possess out-of-doors. The struggle for light 

 is the chief cause of change of habit. It is the adaptation of 

 methods to this change in habit and rapidity of growth which 

 largely determines the good gardener. 



THE CLEMATIS DISEASE. 



A most valuable paper was one by Professor Comstock, of 

 Cornell University, explaining the cause of the fatal Clematis dis- 

 ease, which has so long baffled investigation. One nursery- 

 man in Ohio estimates his loss last year from this disease at 

 $4,000, and the subject is so important that we reproduce the 

 paper almost entire : 



The more striking symptoms of this disease are (1) the 

 leaves suddenly turn black ; then (2) the vine dies down to a 

 spot near the root that has a diseased appearance. Fre- 

 quently, after a period of rest, the plant will take a fresh 

 start, sending up a new shoot from the root. But the life of 

 this growth is of short duration ; for the plant that once dies 

 down is doomed to perish soon. At first sight there are 

 strong reasons for locating the seat of the disease in a limited 

 section of the vine near the ground. This section has a 

 diseased appearance ; the plant dies down to this point ; and 

 later fresh shoots are sent out from below it as if the roots 

 were healthy. It was doubtless these reasons that led Pro- 

 fessor Arthur to look upon a fungus which he found in the 

 plant at this point as the cause of the disease. But my studies 

 of the past two years have convinced me that this fungus 

 simply accompanies the disease, and that the cause of it is 

 something very different. Every grower of Clematis has 

 observed knotty growths of varying size upon the roots of 

 some of the plants. It is in these knots, or galls, that the cause 

 of the disease is to be found. If a gall be cut across and the 

 section examined with a hand lens of moderately high power, 

 there will be found embedded in the abnormal plant growth 

 small, pear-shaped bodies of the same color as the cut surface 

 of the root, but rendered easily visible by their smooth, pol- 

 ished surface. These pear-shaped bodies are found on care- 

 ful examination to be sacs containing a large number of eggs. 

 In fact, each sac is the body of a worm which has become 

 greatly distended by the eggs which have been developed 

 within it. It is these worms cankering the roots of the plants 

 that cause the disease. And, as they multiply rapidly, when 

 soil becomes infested by them the spread of the disease is 

 terrible. I know nurserymen, who a few years ago produced 

 Clematis plants by the tens of thousands, who have been 

 forced to give up their production on account of this disease. 



But more unfortunate than the serious injury caused by 

 these worms to the Clematis, is the fact that they do not con- 

 fine their attacks to this plant. A very large number of 

 species are liable to be attacked by them, and consequently 

 the trouble cannot be overcome by simply suspending the 

 production of this one plant. It is a question in which every 

 horticulturist, whatever he produces, is interested. It seems 

 as if the horticulturist was fated to ever have new battles to 

 right. He became thoroughly aroused long ago to the war- 

 fare against insects ; somewhat later he awoke to the appre- 

 ciation of the importance of plant disease caused by fungi, 

 and now we find another group of animals much lower than 

 insects preying upon plants to a serious extent. 



The animals in question are worms, belonging to the order 

 known to zoologists as the Nematodes, or thread-worms. The 

 species of this order that have attracted the attention of 

 gardeners abroad are commonly known as eel-worms. A good 

 illustration of the order is the " vinegar eel," a minute creature 

 often seen wriggling near the surface of vinegar. The majority 

 of the species are, like the " vinegar eel," harmless, feeding 

 upon dead Or decaying vegetable matter. A few species 

 attack growing plants. The best known of these to readers of 

 the English journals is the one that causes ear-cockles in 

 Wheat in England, and the tulip-root of Oats in the same coun- 

 try ; but more important than either of these is the species 

 that infests the Sugar Beet in Germany. That species and the 

 one infesting Clematis are closely allied, and differ from other 

 forms in the body of the female being pear-shaped, as already 

 described above ; but the two species differ in that the one 

 infesting Sugar Beet does not cause the plant to form galls like 

 that infesting Clematis. 



Both sexes of this species when young are very minute, 

 requiring a high power of the microscope to detect them, and 

 are thread-like in form. They can crawl very rapidly, and 

 it is in this stage that the species is spread from plant to' plant. 

 The males undergo some remarkable changes, but are always 



more or less thread-like. The females, after finding lodging 

 places in the tissues of the roots and becoming fertilized, 

 become distended in a remarkable manner, assuming the 

 pear shape already described, and becoming of sufficient size 

 to be seen by means of a simple lens. 



The range of plants infested by this species of Heterodera is 

 very great. It is already known to attack at least seventy-five 

 species of plants belonging to widely different orders. It is 

 found in diseased roots of Roses ; it is very common in 

 Begonias ; it does a good deal of injury to Cucumbers, Pota- 

 toes and Tomatoes. In the south it is especially destructive 

 to Peach, Grape and garden vegetables, including Cabbage, 

 Turnip, Lettuce, Beet, Parsnip, Egg-plant and Melon. This 

 wide range of food plants is the most discouraging element in 

 the treatment of this disease. In fact, I do not feel that we are 

 in condition to name with any great degree of certainty any 

 plant on which the worms cannot live. In this direction lies an 

 important field for future experiments. When such plants 

 have been determined, the cultivation of them on infested 

 ground, and thus starving the worms out, will be the most 

 practicable way of meeting the evil in the case of field crops. 



A German writer, Professor Kuehn, strongly urges the use 

 of what he terms catch-plants against the species that infests 

 Sugar Beet. He has used Rape as a catch-plant. This is 

 sown on infested fields ; the young worms in the soil pene- 

 trate the roots of the plants. After the roots have become 

 infested, but before the females have begun to produce young, 

 the plants are pulled up and destroyed. In this way several 

 crops of Rape are produced upon the infested field one after 

 another in the same season, each succeeding crop tending to 

 entrap the worms remaining in the soil. But, obviously, the 

 use of catch-plants is a very expensive method of fighting the 

 pests, and yet it is an expense that would be gladly met by the 

 owners of valuable lands if they could feel sure of such results 

 as these reported by Professor Kuehn. Still I think we are 

 hardly ready yet to give definite directions for the use of such 

 plants. It seems to me, however, that the growers of Clematis 

 can at once, without waiting for further discoveries, reduce 

 their losses to the minimum by a little care in the manage- 

 ment of their plant-houses, in the procuring of potting soil 

 and in the choice of fields for planting out. 



The conditions in some of our establishments where Clema- 

 tis is grown are those most favorable for the multiplication 

 and perpetuation of the disease. The benches upon which the 

 pots stand are covered with gravel or coal ashes, which is 

 changed at infrequent intervals; the roots of the diseased 

 plants pass through the hole in the bottom of the pot and 

 ramify in the gravel or ashes, and the worms follow the roots, 

 infest them, and this soil becomes a breeding place for the 

 pest. When another lot of plants is placed upon such soil, 

 obviously in a short time these plants will become diseased. 

 It is recommended, therefore, that between each two lots of 

 plants the soil be carefully removed from the benches and 

 placed where it will not contaminate other crops ; that before 

 renewing the soil the benches be thoroughly washed with lye 

 so as to destroy any worms that may be lodged in the cracks ; 

 that the soil for potting be carefully selectee! so that it shall 

 not be a source of infection ; that in planting out great care 

 be taken to make sure that it be done on land which is free 

 from this worm ; if any roots of any kind are found in the soil 

 which have unnatural swellings upon them, the field should 

 not be used, as there will be a strong probability that such 

 swellings are galls made by this worm ; and finally, until a 

 grower is able to produce only healthy plants he should not 

 use root-grafts, for roots that are apparently healthy often 

 contain the worms. 



THE EMBELLISHMENT OF PUBLIC PLEASIRE-GROUNDS. 



The paper on this subject, by Mr. William McMillan, Super- 

 intendent of the Buffalo parks, was one of substantial merit, 

 and its value was made so clear by impressive delivery 

 that the effect on the audience was striking. After speaking 

 of the necessity of having a consistent plan, Mr. McMillan in- 

 sisted upon thoroughness of construction ; everything should 

 be of the most durable character, since the admission of 

 makeshift and temporary work always proves costly in the 

 end on account of the greater cost of maintenance. In a con- 

 sistent plan all features will not only be in proper harmony 

 with each other, but nothing will be introduced that cannot 

 under ordinary municipal conditions be easily maintained in 

 good condition at all times. For instance, the location, width 

 and alignment of drives and paths will combine to the best 

 advantage, gracefulness of proportion and convenience in use. 

 The sinuosity of a walk, if unnecessary or unnatural, will 

 surely tempt pedestrians to make a cross-cut track at every 



