642 



THE GARDENERS' CHRONICLE OF AMERICA. 



the ostioles or mouths of the necks will show as dark 

 spots at the ends of the surface papillae. There is con- 

 siderable variation in the length of the surface papillae, 

 the difference being due to varying amounts of moisture, 

 those which develop with an abundance of moisture 

 showing especially long necks, while with scarcity of 

 moisture the papilte remain short. 



The spore-sacs formed in the perithecia contain tlie 

 ascospores. Each sac produces eight two-celled spores 

 arranged generally in two irregular rows. These 

 spores have a volume about fifty times as great 'as 

 that of the pycnospores. They are not extruded ordi- 

 narily in masses from the perithecia, but under favor- 

 able conditions of moisture and temperature the spore- 

 sacs rise to the ostiole and explode, forcing the spores 

 into the air. If a glass slide is suspended Ys inch 

 or slightly more above the surface of some mature 

 perithecial pustules moistened in water and kept at a 

 temperature not under 65 degs. F., large numbers of 

 ascospores will be expelled and will adhere to the slide. 

 A similar expulsion of ascospores takes place in nature 

 whenever conditions are favorable. 



The ascospores have ben designated as "winter 

 spores." Their time of maturing, however, appears to 

 depend more upon the age of the lesion than upon 

 the season of the year. Maturing perithecia may be 

 found at any season of the year, although they are 

 perhaps more abundant in the fall and winter than at 

 other seasons. Successive crops of perithecial pustules 

 may be found on a single lesion which has persisted for 

 a number of years. The blight fungus may spread 

 throughout the bark of a blight-killed tree and con- 

 tinue to produce fruiting pustules, or perithecial pus- 

 tules may be produced in abundance in the crevices 

 of the bark of fallen logs. 



THE SPREAD OF THE DISEASE. 



The cause of infections. — New infections, whether 

 in sound trees or in those already diseased, are caused 

 by the establishment of the vegetative body or my- 

 celium of the fungus in the tissues. This mycelium 

 originates from either pycnospores or ascospores. 

 If this germination takes place in some wound which 

 penetrates the outer brown bark, the fungus readily 

 establishes itself and begins to grow through the 

 tissues of the bark in much the same way that it is 

 growing in the culture medium. An infection can be 



caused then by either a single ascospore or a single 

 conidiospore if they are carried and lodged in a fa- 

 vorable location. A large percentage of the new in- 

 fections appear to be definitely related to some me- 

 chanical injury, but there are some evidences that 

 natural cracks and fissures may also be the avenue of 

 entrance. 



Natural agencies in dissemination. — The pycno- 

 spores or the ascospores must be carried from one 

 part of a tree to other parts, or from tree to tree, if 

 new infections are to result. Present investigations 

 point to the fact that ascospores which are forcibly 

 e-xpelled into the air during the moist and warm 

 periods of the year play a very important part in the 

 spread of the disease, since they can be carried by the 

 air currents. It can also be definitely stated that 

 conidiospores are washed down during every rain, even 

 the cold rains of winter, in countless numbers from 

 every lesion that has reached the spore-producing stage. 

 It seems probable, then, that conidiospores play a 

 very important part in the spread of the disease 

 throughout a tree after it once becomes infected. Rain 

 and wind are undoubtedly the most important natural 

 agents in the dissemination of spores. 



The part which birds, insects and other animals 

 play in the scattering of spores is at the present time 

 somewhat problematical. The few tests reported up 

 to date have given only negative results. (See Bulle- 

 tin No. 3 of the Pennsylvania Chestnut Tree Blight 

 Commission.) From investigations now in progress 

 it may be definitely stated that a single downy wood- 

 pecker has been found to be carrying as many as 

 657,000 pycnospores. 



Artificial agencies. — It has been definitely shown in 

 numerous cases that the shipment of infected chestnut 

 nursery stock has been responsible for the introduc- 

 tion of blight into a new region. After it is once in- 

 troduced, natural agencies may be responsible for the 

 scattering of the spores. 



The shipment of chestnut products of various kinds, 

 such as logs, wood, posts, poles, etc., made from 

 blight-affected trees may also be responsible for 

 spreading the disease, since the mycelium may retain 

 its vitality in blighted bark or wood for long periods 

 and produce new crops of pycnidia very soon after 

 moisture is supplied, or spores may be scattered from 

 pustules formed previous to shipment of the products. 



A Complicated Combination 



By N. M. Edgerton. 



The factors having to do with successful agriculture 

 are many and various in character, and to be su- 

 premely successful in unlocking the storehouse of na- 

 ture's wealth one needs to know the whole combina- 

 tion. Not only are there many factors involved in the 

 successful production of any sort of crop, but each 

 factor is in itself of a complicated nature. For in- 

 stance, there is the factor of soil. Soil is not made up 

 of dead, inert matter merely, as the uninformed might 

 properly suppose. Far from being dead, inert matter, 

 soil abounds in life. The more active this life, the 

 greater its productivity. 



Now there are certain conditions in soil which pro- 

 mote activity in soil life, and there are other condi- 

 tions which tend to inertia or inactivity in this life. 



To be entirely successful, therefore, writes N. M. 

 Edgerton in Vegetable Grower, in promoting and 



maintaining the greatest degree of soil productivity, 

 one must possess the necessary knowledge whereby 

 the required soil conditions may be promoted and 

 maintained. To know just what conditions are right 

 and what are wrong, and just what processes will 

 bring about and maintain right conditions, this is the 

 great desideratum. Chief among the factors promot- 

 ing conditions favorable to soil life I may mention soil 

 drainage and aeration, humus and moisture content, 

 and richness in the elements of plant food, in a form 

 available for plant use. 



A water-logged soil, that is to say, a soil upon which 

 water stands for any length of time, either on the sur- 

 face or in first few inches of surface soil can- 

 not be in a condition favorable to the welfare of most 

 kinds of plant life. Now, soils that are exceptionally 

 fertile are filled with minute organisms whose office 



