DISEASES. 51 



to become an imi)ortant factor in determining the limits of tlnj artKicial cultivation of this species. 

 At the time of planting, deciduous trees are not in leaf, and accordingly there is but little evap- 

 oration of water, while the leaf surface of conifers is exposed then as much as ever to the drying 

 effects of the atmosphere, often resulting in their death before they are fully established in the soil. 

 It is for this reason and because of the general lack of a sufficient amount of atm<)spli('ri(! mois- 

 ture that comparatively slight success has attended the cultivation of the White i'ine on the 

 plains west of the Mississippi. The raw winds from the Atlantic again have been found to be 

 much more injurious to this siiecies than to the Pitch Pine (rinus rhjiiJa), iind tlie latter is there- 

 fore decidedly preferable for planting in the immediate vicinity of the coast. 



DISEASES 

 EFFECT OF HEAT AND DROUGHT. 



In Germany, i)lantations of White Pine thirty-tive to forty years old have suffered much injury 

 from a disease which appears to be occasioned by unusual heat and drought, and which was par- 

 ticularly severe after the hot, dry summer of 1876.' The disease manifests itself externally by 

 dried up patches on the trunks, the spots being largest 3 to 6 feet from the ground, gradually 

 running out above and below this, and often reaching a height of 15 to 18 feet. The spots may be 

 only an inch or two wide, but frequently the bark is dead nearly around the entire trunk. As 

 a rule, these dead spots are on the south and west sides of the tree. The wood is often i^enetrated 

 by larviTJ of insects, but these are not the cause of the disease, since in many cases they are not 

 present. 



Dr. li. Ilartig, from a comparison of specimens and study of the disease in question, concludes 

 that it is due to extreme dryness and that the White Pine can not be trusted to endure such 

 extremes. He further states that it suffers greatly from dry air even in the winter time. 



PAKASITIC DISEASES. 



The White Pine is subject to a number of parasitic diseases, some of which attack it when 

 growing spontaneously in the forest, while others are highly destructive to the tree in culti\atiou, 

 especially in Europe under changed climatic conditions. A few only of the best known of these, 

 including several due to fungi, will be considered in detail. 



(1) Agaricus mellens Vahl. — This fungus, of common occurrence in the United States as well 

 as Europe, is exceedingly destructive to coniferous trees, the W^hite Pine in particular suffering 

 greatly from its attacks. It also fastens upon various deciduous species as a parasite, attacking 

 living trees of all ages, but living as well upon dead roots and stumps and on wood that has 

 been cut and worked uj), occurring frequently on bridges, railroad ties, and the like, and causing 

 prompt decay wherever it has eff'e<-ted an entrance. The most consi)icuous part of the fungus is 

 found frequently in the summer and tall on the diseased parts of the tree or timber infested by it. 

 It is one of the common toadstools, this particular species being recognized by its yellowish color, 

 gills extending downward upon the stem, which is encircled a little lower down by a ring, and by 

 its habit of growing in tutts or little clumps of several or many individuals together (I'l. XII, 

 1 and 3). It is also particularly distinguished by the formation of slender, dark-colored strings 

 (PL XII, 2 and 5), consisting of compact mycelium, from which the fruiting parts just described 

 arise. These hard root-like strings (called rhizoinorphs) extend along just beneath the surface 

 of the ground, often for a distance of several feet, and penetrate the roots of sound trees. By 

 carefully removing the bark from a root thus invaded the fungus is seen in the form of a dense, 

 nearly white, mass of mycelium (PI. XII, 5, c), which, as the parts around decay, gradually pro- 

 duces again the rhizomorphs already described. These ihizoniorphs are a characteristic part 

 of the fungus. Occurring both in the decayed wood, from which they spread to the ailjaccnt 

 parts, and extending in the soil from root to root, they constitute a most effective agency in the 

 extension of the disease. 



The symjttoms of the disease are marked, and, taken together, sufficiently characteristic to 

 admit of its ready recognition. External symptoms, to be observed especially in young specimens 



' Hartig. Unterauchuugeu aiis dem Forstbotanischeu lustitut zu MUncheu, 1883. 



