in 



THE AGKICULTURAL NEWS. 



March 19, 1910. 



FUNGUS NOTES. 



Fig. 

 Oil 



9. ZOdSI'OEES OF 



idiiim limxsicac. 



THE CHIEF GROUPS OF FUNGI. 

 Paet II. 



THE SIMPLEST KOR.M OF PLANT LIFE. All the plOCeSSeS of 



life .ire invariably connected with a peculiar colourless, jelly- 

 like substance of a very complicated structure, and containing 

 very many different chenrical compounds. This substance is 

 known as protoplasm. Generally, a small portion of this, 

 which is even of a more complicated nature than the rest, 

 is sejiarated from it, and is denser. It is usually spherical 

 in shape, and is known as the nucleus. The nucleus is that 

 part which controls all the different physical and chemical 

 processes which take place in the rest of the protoplasm. 

 Many of the simplest forms of life, therefore, consist of a more 

 or less shapeless mass of the jelly-like substance of a very 

 minute size, which contains one or more nuclei. Such forms 

 of life are most frecjuently met with 

 in water, as there they are less 

 exposed to sudden changes of tem- 

 perature, or to any danger of 

 drought, or of encountering strong 

 solutions of chemical substances, 

 which might injure the proto- 

 plasm. Frequently, these minute liv- 

 ing bodies are of a definite egg- 

 shape, and have attached to their sharper end one or more 

 very fine, thread-like outgrowths. Such a thread is known 

 as a cilium. It possesses the power of independent move- 

 ment, and by lashing about in the water 

 enables the organism to swim, in this 

 way giving it a better chance of obtain- 

 ing its food. If, to such an organism 

 as the one just described, the green 

 colouring substance known as chlorophyll 

 is added, we obtain the very simplest 

 form of plant known. Such a plant is 

 complete in itself, and can obtain all its 

 food-supplies from the chemical substan- 

 ces dissolved in the water in which it 

 lives. It swims about for some time, 

 until it attains a certain size, after which 

 it divides longitudinally down the mid- 

 dle into two plants, each containing 

 a nucleus formed from the original one, 

 together with half of the original protop- 

 lasm and chlorophyll. 



Now the fungi, as Is well known, 

 are plants which have lost the i)ower of 

 forming their own chlorophyll, and 

 consequently they cannot obtain carbon 

 from carbon dioxide gas. Thus they 

 must get it from other organisms, 

 either dead or alive. If such a simple 

 form of plant as has been described 

 above were deprived of its chlorophyll 

 simplest possible form of fungus. Now, 

 to live in the interior of some uther plant, the naked proto- 

 plasm might be e.\.posed to harmful chemical substances given 

 off by the host plant. To guard against this, it covers itself 

 ■with a firm outer coat, or wall, which is very resistant to 

 such substances. These fungi, consisting of a cell wall, 

 protoplasm, and a nucleRS, and nothing further, are found 

 among the members of the group Chitredineae. Some 



Fig. 11. Ascus 



WITH ASCOSPOKES. 



it would be the 

 if this fungus had 



Fii^- 10. Sporangium of 

 Olpidiuin brassicae. 



of these fungi live in the cells of various higher plants, 

 and cause a considerable amount of damage to them; for 

 example, Olpidium hrasdcae, which causes a disease of young 

 cabbages. The full life-history of the fungus is as follows: 

 It consists of a naked mass of protoplasm, with a nucleus and 

 one whip-like outgrowth, or cilium, attached to its pointed 

 end. It swims about in a drop of water on the surface of 

 the cabbage, and eventually bores its way into the tissues, 

 becomes spherical, and covers itself with a cell wall. It 

 grows, and finally produces a long tube, which penetrates to 

 the .surface of the host plant, and projects into any drops of 

 water that there may be on the surface, ileanwhile, the con- 

 tents of the spherical portion have divided up into numerous 

 minute, free-swimming bodies or zoospores (Fig. 9), each 

 exactly like the first stage of the origmal plant. The central, 



spherical portion of the parent 

 fungus, in which the zoospores 

 were formed, is known as a 

 xporawjium (Fig. 10). The 

 zoospores are discharged through 

 the neck, swim about as before, 

 and finally penetrate the host 

 plant again and repeat the life- 

 cycle. 



The next step in the develop- 

 ment of the fungi from the 

 simjilest forms, is the formation 

 of long fine threads, which pene- 

 trate the substratum in search- 

 of food. These threads are usually without cross walls in 

 the simplest forms, but possess them in the more elaborate 

 ones. Each thread is known as a hypha, and the whole 

 system of them as the mycelium. The 

 reproductive organs are oiily boine on 

 certain parts of these threads. 



The mr>re elementary fungi require 

 moisture for their reproductive purposes, 

 and in this way show their relationship with 

 the more p;imitive form of plant which 

 lived in water. In the course of ages, 

 however, these reproductive methods be- 

 came very much altered, so as to enable the 

 plants to live more conveniently on land, 

 and to reproriuce themselves independently 

 of the presence of moisture. How this came 

 about will be shown in discussing the var- 

 ious grou|)S. 



THE MAIS (IROUPS OF FUNGI. The 



fungi are <livided into four main groups, 

 chiefiy in accordance with the characters 

 of their reproductive organs. These groups 

 are as follows: — 



The Phvcomycetks. — The vegetative 

 mycelium of the members of this group 

 never forms a compact mass, but usually 

 branches in the tissues of the plant or 

 animal upon which these fungi generally 

 live. Some of them exist saprophytically 

 on decaying substances, but the majority are 

 parasites. There are two forms of reproduction: the first by 

 means of conidia, Avhich germinate either by dividing up to 

 form free-swimming spores, or zoospore.s, as described for the 

 Chitredineae, or by producing a mycelial tube direct; the 

 second by means of thick-walled, resting spores produced as 

 the result of a sexual process. 



The Ascomvcetes. — In this group, the mycelium may 

 be either entirely buried in the substratum, or may fornir 



Fk;. 1-2. B.A.sir.- 



lUM, WITH 

 SPORIDIA. 



