DISEASES. nS 



In the Scotcli Pine a great amount of resin is iirodiict-d, ami tliis, aftcumulating in tlie lower 

 part of tliestcni, probably a<!ts as a barrier to tlio growtli of the mycelium upward. In tlic Wliite 

 Tine the fun{j:us extends much farther in the trunJi. 



PI. XII, 7, represents a stump of White Pine tliat has l)(!en attacked \}y J'oli/porus aunosiis. 

 The heart is surrounded by decayed wood and spots Idled with masses of resin. PI. XII, f), 

 represents parts of adjacent wood elements of Norway .Spruce after they have beeu acted ujmn 

 by the fungus; tlie mycelium hyphai and spores, highly magnified, are represented in ]0 of the 

 vsame plate. 



(3) Goleosporium senecionis Pers. — This fungus, under the na-me of "])ine blister," infests 

 various species of ])ines, growing in the a^cidium stage on both leaves and bark, and sometimes 

 ])roving very destru(^tive. When growing on the leaves it affects but little the vitality of the tree, 

 but is highly injurious when the bark is the place of attack. It penetrates the bark, apparently 

 through wounds occasioned by insects, woodpeckers, or other agencies, and its mycelium spreads 

 through the cortical parenchyma and bast, and into the wood to the depth of several inches, 

 passing through the medullary rays. 



Under its iuHuenco the starch and other cell contents disappear and a resinous substance 

 collects in their stead, a mass of dead tissue soon taking the place of the living cells. This cliange 

 of the cell contents results in a great accumulation of resin, which often exudes in large quantities 

 from tlie diseased parts of the tree. 



The mycelium is perennial, extending itself through the stem from year to year, particularly 

 in a longitudinal direction. Where it is present the growth of the stem is prevented and the 

 formative materials are diverted to the opposite side of the stem, causing there a greatly stimulated 

 and abnormal growth. The death of the leader often results, especially in dry summers, for the 

 reason that the wood, thus choked with resin, is iinable to supply it with sufticient water. 



The researches of Wolf lead to the conclusion that this parasite of the pine lives in the form 

 known as Goleosporium Hcnecionlx on various species of Senecio, and that it is communicated to 

 pine shoots from them. He proposes the extermination of these hosts as a preventive measure. 

 Later investigations of Kleebahn go to show that a blister rust which he observed badly aftecting 

 the bark of Finun strobus, in the neighborhood of Bremen, is caused by a closely related parasite 

 form which he names I'eridermium strobi, and considers to be the a-cidium stage of Cronartlum 

 rihicola. 



All these fungi have probably caused far more destruction of timber than casual observation 

 would indicate, but the limited extent to which artificial cultivation of forests has thus far been 

 carried on in this country gives comparatively few exact data regarding them. The facts, as above 

 stated, have therefore been drawn largely from the works of Hartig and other European authorities. 

 With increasing cultivation of timber and probable increase of such diseases, their investigation 

 and the employment of protective measures must necessarily receive far more attention. 



Several diseases attributable to the action of fungi, but as yet im2)erfectly investigated, are of 

 frequent occurrence in this country. One of these, known as "damping off," characterized by the 

 sudden decay of seedlings at the surface of the ground, is common in nurseries, and attacks young 

 plants of different kinds, the White Pine among them. 



The disease is most prevalent in plants growing in a damp soil in a warm, moist atmosphere. 

 As observed in the Ann Arbor (Michigan) greenhouses for several years in various i)lants proi)a- 

 gated from slips, the disease appears a few days after the slijjs are set, giving the lower part of 

 the stem a wet, unhealthy api)earance, which extends to the lower leaves, particularly where these 

 touch the sand in which they are growing. Upon taking up the specimens, the i)arts affected are 

 found to be in the early stages of decay, and penetrated throughout, even in the interior of the 

 epidermal appendages, by the branching filaments of a fungus. The fungus appears to live in the 

 sand in which the plants are propagated, and to run in it from one to another, resulting often iu 

 the rapid destruction of the ])lants in the bed. 



"Damping off" is due to the action of several different parasitic organisms, of which the 

 pottingbed fungus, I'yihium de btiri/aiiuiii Hesse, is one of the most common, though a number of 

 other species have been shown to be capable of producing the disease. Tlie relief measures 

 recommended by those who have studied the disease are the use of fresh soil free from decaying 



