Octabsr 1, 1868. ] 



JOUBNAI. OP HORTICULTURE AND COTTAGE GAFDENEB. 



245 



assumed by combination of these elements. The fruits of 

 Fungi are designated spores. Sporules, sporidia, sporidiola, 

 are synonymous terms, and should be disused. At the ends 

 and along the edges of mycelium threads it is common to find 

 rounded or oval bodies, having much the appearance of, and 

 commonly designated, spores, from which, however, they should 

 be distinguished aa being merely buds, hero called conidia. 

 The mycelium is so much alike in all cases that it is practically 

 hopeless to seek to distinguish Fungi by any characters resident 

 in this part of their structure. The place of growth and 

 arrangement of parts due to this cause, furnish useful provisional 

 characters. Dimorphism — the occurrence of the same plant in 

 two or three different states — has been well authenticated in 

 several Fungi, and is on good grounds suspected to occur in 

 more. The occurrence in many plants of cutaneous diseases 

 from the presence of parasitic Fungi is in itself a fact of interest, 

 when it is remembered that certain of the skin diseases affect- 

 ing mankind are due to the same cause. Is it possible that 

 transplantation from one to the other may occur ? The pre- 

 sent state of science seems quite to favour such a view, 

 and the subject has been thought to possess sufficient in- 

 terest to justify its being thus brought before the notice of 

 the profession. 



The existence in many of the higher plants of diseases 

 accompanied with parasitic Fungi, and unquestionably induced 

 thereby, has led to the attempt to ascertain how far careful 

 study of these plant parasites may throw light on some difficult 

 questions connected with analogous structures found in certain 

 diseases of the human skin. The greater simplicity in the 

 conditions of vej;etable growth, and the readiness with which 

 its processes can be observed under the microscope, lead to a 

 reasonable expectation that in time questions relating both to 

 practice and to hygiene may be assisted in their solution by 

 such study. 



The epiphyllous Fungi attack plants entirely irrespective of 

 the health of their "hosts," which, however, when attacked, 

 manifest symptoms of irritation and ill health in various ways, 

 due to chemical changes set up in them by the parasite, and 

 altering their nutrition. " Redness and swelling " are with 

 some very marked {e.g., J'ieidium compositarum Lapsani, 

 Trichobasis beta;, Aregma bulbosum), and there are good 

 reasons for supposing that heat is also a concomitant. 

 These indications of sufiering from the presence of the parasite 

 correspond strikingly with the classical definition of inflam- 

 mation. 



The parts of plants are not always invaded alike ; some — • 

 indeed, most of the Fungi in question — prefer to nestle in the 

 tissues immediately beneath the cuticle of the leaves on their 

 lower surface, others on the stems k.jr., Puceinia graminis, 

 Ustilago hypodytes), whilst a few invade one or other of the 

 parts composing the flower (smut and bunt). 



The effects of the Fungi differ greatly on different plants, 

 some of which are sufficiently hardy to recover rapidly ; but 

 the softer herbaceous plants, through sap-drainage and de- 

 terioration, are usually quickly destroyed. In their mature 

 condition they occur on leaves of different ages, according to 

 the genus, and, in some cases, the species, .^cidium in its 

 different forms almost always inhabits the young leaves ; the 

 Uredo fruits mostly affect older leaves ; the Puccinije, leaves 

 whose moat vigorous condition is past ; and in two species, 

 occurring on the stems respectively of Hemlock and Asparagus, 

 the fruit is not matured until winter, after the stalks of the 

 plants have been long dead. It is not yet quite settled whether 

 the Erysiphei pass into the tissues ; in their oidial condition 

 {e.g., Vine-blight), they appear on the most vigorous leaves, 

 and some pass to the state of mature fruit, with very slight, if 

 any, visible disturbance to the tissues of their host. Plants 

 growing near together are often attacked by the same species 

 of Fungus. The explanation of the fact is easy. The spores 

 from an infected plant of the previous year, or motile gemmu; 

 just thrown off by members of the genera Cystopus, Perono- 

 spora, Oidium, however brought, whether carried by the wind 

 or by insects, present in the soil, in or upon the seed, do un- 

 doubtedly spread in the way of a contagion induced by pre- 

 existing germs. 



Care must be taken not to confound the action of true 

 parasites with that of the Fungi appearing on dead or dying 

 vegetable matter. The first grow with the growth of their 

 hosts, and in their vegetative portion, die at and through their 

 death ; with some there are evident precautions to prevent 

 premature injury to the tissues of an infected plant. The latter 

 ieed upon, and reduce to simpler elements^ decaying matters 



which would otherwise cumber the ground and even prove 

 noxious : these belong to totally different tribes. 



The parasitic Fungi are apt to recur with so much regularity 

 year by year in the same spots that, when their habitats have 

 onco been found, a supply from the same place may at the 

 right period be ealculattd on with tolerable certainty. The 

 presence of fungus-mycelium may be readily demonstrated (if 

 present) in the apparently healthy tissues of healtliylooking 

 plants. Parasites of this class produce changes differing 

 greatly in appearance according to the kind of plant attacked 

 and the invader — hectic red in some, sickly pallor in others, 

 blackness followed rapidly by cffinsive decay in a third division. 

 These appearances are so chnracteribtic that the educated eye 

 may often diagnose the kinds met with in a quiet stroll through 

 country lanes, by their effects, with as much ease and certainty 

 as in practice ; the types of disease presented will not seldom 

 betray their nature by their peculiar jilii/iiqtic. Seasons largely 

 influence the prevalence or scarcity of these Fungi ; moistme 

 favours their growth. As yet the present exceptional summer 

 has produced large numbers, whilst some kinds, found but 

 sparingly hitherto by me, have been abundant notwithstanding 

 the heat and drought. Special meteorological conditions are 

 known to largely influence their growth ; a close still air like- 

 wise : hence their luxuriance often in shady spots, and on plants 

 sheltered from the breezes by rank, thickly crowded herbage. 

 The Fungi which attack plants placed in situations which are 

 (for them) unusually moist (as Ferns in a wet Fern-case, or 

 plants in a damp greenhouse) are quite different from those to 

 which they would have been liable in their native habitats. It 

 is doubtful if the feeble health of the vegetables have any direct 

 effect in inducing the attacks of parasitic Fungi, as it is certain 

 that intestinal worms develope when their germs are placed in 

 favourable situations, and that the health of their hosts has 

 nothing to do with facilitating access to such places. The 

 stale of weather favouring growth of the Fungi is unfavourable 

 to healthy life in the higher plants ; hence the rapidity with 

 which the latter fall a prey to the abounding parasitic Fungi in 

 unhealthy seasons. During winter the epiphyllous Fungi 

 disappear, but the first fine days of spring rapidly call forth 

 again their latent vitality ; with the leaves they come, and with 

 them disappear. Afew (Melampsoia^) which appear as "rusts" 

 in the autumn continue their growth on the decaying leaves, in 

 damp spots, on which, in the following spring, they are found 

 to have attained to a higher type of structure. Evergreens are 

 almost free from them ; five only are known to be subject to 

 their attacks in this country — all rare except perhaps the 

 Puceinia buxi. This comparative immunity may be due in 

 measure to the density of their cuticles. 



It may be stated as a general rule that each species of plant 

 has its own parasitic Fungus, except in seme of the larger 

 natural orders, as the LegumincFai, Compositsr, &c., where the 

 same parasitic Fungus will be found attacking many of the 

 specific forms therein included. It is rare to find plants 

 belonging to different natural orders attacked by the same 

 species of Fungus. There are many species, and even genera, 

 of plants which have not been ascertained to be liable to para- 

 sitic Fungi. It is difficult to suggest any reason for such 

 exemption. Hairiness of the surface will favour the arrest of 

 floating spores, smooth polished surfaces the contrary. As in 

 the case of galls, so it is again here. An abundant supply of 

 nutritive juices, with thin cuticle, favours their production: 

 hence the mutual preference for young leaves, stalks, and 

 twigs in a state of active growth and sap-circulation. It is 

 well known that the cellular are the least specialised of the 

 tissues of plants, the woody and vascular the most complex; 

 and it may not bo without interest to remark that the first 

 stages of decay are attended by Fungi of the simplest types — 

 Fusarium, Penicillium, Mucor, Botrytis — whilst the reduction 

 of the more specialised tissues seems to demand Fungi of more 

 elaborate organisation — Spha'iia> (ascigerous Fungi with 

 corneous envelopes), Peziziu (naked ascigerous Fungi) — and in 

 vastly greater variety of .specific type. As during life one 

 plant furnishes oil of lavender, a second quinine, and a third 

 strychnia, so during life will the tissues of the Potato seem 

 only adapted to nourish its peculiar Percnospora, Corn its 

 Puceinia, Mint its jEcidium, yet after death will all alike 

 be preyed upon by the same kinds of Fungus, and suffer 

 alike. 



There are 235 reputed species of epiphyllous Fungi described 

 as native to Britain, but several of the supposed genera are 

 now considered by the best authorities to be only transitory 

 conditions, so that the number is certain to be eventaally 



