2Q3 



NA TURE 



[July 26, 1888 



in the aforesaid membrane of contiguous barren spores. 

 If we examine older sEcidia, it will be found that this 

 membrane bursts also at length, and the spores escape. 



Similar sections across a Spermogonium exhibit a 

 structure which differs slightly from the above. Here 

 also the hyphae in the leaf turn upwards, and send 

 delicate branches in a converging crowd beneath the 

 epidermis ; the latter gives way beneath the pressure, and 

 the free tips of the hyphae constrict off very minute spore- 

 like bodies. These minute bodies are termed Spermatid, 

 and I shall say no more about them after remarking that 

 they are quite barren, and that similar sterile bodies are 

 known to occur in very many of the fungi belonging to 

 this and other groups. 



Sections through the sEtidia and Spermogonia on the 

 cortex present structures so similar, except in minute 

 details which could only be explained by lengthy descrip- 

 tions and many illustrations, that 1 shall not dwell upon 

 them ; simply reminding the reader that the resemblances 

 are so striking that systematic mycologists have long 

 referred them to a mere variety of the same fungus. 



Now as to the kind and amount of damage caused by 

 the ravages of these two forms of fungus. 



In the leaves, the mycelium is found running between the 

 cells (Fig. 33, //),and absorbing or destroying their contents : 

 since the leaves do not fall the first season, and the myce- 

 lium remains living in their tissues well into the second year, 

 it is generally accepted that it does very little harm. At 

 the same time, it is evident that, if very many leaves are 

 being thus taxed by the fungus, they cannot be supplying 

 the tree with food materials in such quantities as if the 

 leaves were intact. However, the fungus is remarkable in 

 this respect — that it lives and grows for a year or two in the 

 leaves, and does not (as so many of its allies do) kill them 

 after a few weeks. It is also stated that only young pines are 

 badly attacked by this form : it is rare to find dLcidia on 

 trees more than twenty years or so old. 



Much more disastrous results can be traced directly to 

 the action of the mycelium in the cortex. The hyphae 

 grow and branch between the green cells of the true cortex, 

 as well as in the bast-tissues beneath, and even make their 

 way into the medullary rays and resin-canals in the wood, 

 though not very deep. Short branches of the hyphae 

 pierce the cells, and consume their starch and other con- 

 tents, causing a large outflow of resin, which soaks into the 

 wood or exudes from the bark. It is probable that this 

 effusion of turpentine into the tissues of the wood, cam- 

 bium, and cortex, has much to do with the drying up of 

 the parts above the attacked portion of the stem : the 

 tissues shrivel up and die, the turpentine in the canals 

 slowly sinking down into the injured region. The drying 

 up would of course occur if the conducting portions are 

 steeped in turpentine, preventing the conduction of water 

 from below. 



The mycelium lives for years in the cortex, and may be 

 found killing the young tissues just formed from the cam- 

 bium during the early summer : of course the annual ring 

 of wood, &c, is here impoverished. If the mycelium 

 is confined to one side of the stem, a flat or depressed 

 spreading wound arises ; if this extends all round, the 

 parts above must die. 



When fairly thick stems or branches have the mycelium 

 on one side only, the cambium is injured locally, and the 

 thickening is of course partial. The annual rings are 

 formed as usual on the opposite side of the stem, where 

 the cambium is still intact, or they ars even thicker than 

 usual, because the cambium there diverts to itself more 

 than the usual share of food-substances : where the 

 mycelium exists, however, the cambium is destroyed, and 

 no thickening layer is formed. From this cause arise 

 cancerous malformations which are very common in 

 pine-woods (Fig. 34). 



Putting everything together, it is not difficult to explain 

 the symptoms of the disease. The struggle between the 



mycelium on the one hand, which tries to extend all round 

 in the cortex, and the tree itself, on the other, as it tries 

 to repair the mischief, will end in the triumph of the fungus 

 as soon as its ravages extend so far as to cut off the water- 

 supply to the parts above : this will occur as soon as the 

 mycelium extends all round the cortex, or even sooner if 

 the effusion of turpentine hastens the blocking up of the 

 channels. This may take many years to accomplish. 



So far, and taking into account the enormous spread 

 of this disastrous disease, the obvious remedial measures 

 seem to be, to cut down the diseased trees — of course this 

 should be done in the winter, or at least before the spores 

 come — and use the timber as best may be ; but we must 

 first see whether such a suggestion needs modifving, after 

 learning more about the fungus and its habits. It appears 

 clear, at any rate, however, that every diseased tree 

 removed means a source of ^cidiospores the less. 



Probably everyone knows the common groundsel, which 

 abounds all over Britain and the Continent, and no doubt 

 many of my readers are acquainted with other species of 

 the same genus (Seneeio) to which the groundsel belongs, 

 and especially with the ragwort {Seneeio Jacobaa). It 

 has long been known that the leaves of these plants, and 

 of several allied species, are attacked by a fungus, the 

 mycelium of which spreads in the leaf-passages, and gives 

 rise to powdery masses of orange-yellow spores, arranged 

 in vertical rows beneath the stomata : these powdery 



Fig. 34. — Section across an old pine-stem in the cancerous region injured by 

 Peridermium Pint (var. corticola). As shown by the figures, the stem 

 was fifteen years old when the ravages of the fungus began to affect the 

 cambium near a. The mycelium, spreading in the cortex and cambium 

 on all sides, gradually restr.cted the action of the latter more a .d more l 

 at thirty years old, the still sound cambium only extended half-way 

 round the stem — no w.:od being developed on the opposite side. By 

 the time the tree was eighty years old, only the small area of cambium 

 indicated by the thin line marked 80 was still alive ; and soon after- 

 wards the stem was completely " ringed," and dead, all the tissues being 

 suffused with resin. (After Hartig.) 



masses of spores burst forth through the epidermis, but 

 are not clothed by any covering, such as the /Ecidia of 

 Peridermium Pitii, for instance. These groups of yellow 

 spores burst forth in irregular powdery patches, scattered 

 over the under sides of the leaves in July and August: 

 towards the end of the summer a slightly different form ot 

 spore, but similarly arranged, springs from the same 

 mycelium on the same patches. From the differences in 

 their form, time of appearance, and (as we shall see) 

 functions, these two kinds of spores have received dif- 

 ferent names. Those first produced have numerous 

 papillae on them, and were called Uredospores, from their 

 analogies with the uredospore of the rust of wheat 

 the second kind of spore is smooth, and is called the 

 Teleatospore, also from analogies with the spores producec 

 in the late summer by the wheat-rust. The fungus whicl 

 produces these uredospores and teleutospores was 

 named, and has been long distinguished as, Coleosporiuiii 

 Senecio7iis (Pers.). We are not immediately interested ii 

 the damage done by this parasite to the weeds which it 

 infests, and at any rate we might well be tempted tc 

 rejoice in its destructive action on these garden pests 

 is sufficient to point out that the influence of the myceliur 

 is to shorten the lives of the leaves, and to rob the plant of 

 food material in the way referred to .generally in my last 

 article. 



What we are here more directly interested in is the 



