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THE AGRICULTUKAL NEWS. 



March 5, 1910. 



FUNGUS NOTES. 



TEE CHIEF GBOUPS OF FUNGL- 

 Pakt I. 



The followincj spries of articles is intended to give 

 a short account ot ilie chi-'f groups of fungi, and of the 

 characters (both those as seen by the naked eye and 

 those as viewed under the microscope) by means 

 of which they are separated from one another. Any 

 points of interest that occur in the life-cycle of mem- 

 bers of the different groups will also be described. 

 The series should be read in conjunction with the three 

 articles on fungi uublished in the A(jrii-idtural J\cws, 

 Vol. VIII. pp. 251, 2G7 and 28.3. It'is hoped that they 

 will be of general interest and also of assistance to 

 those taking the Courses of Reading, as helping lo throw 

 light on the true nature of a fungus, on the different 

 forms under which these plants may appear, and on 

 the various types of injury the}- may inflict upon the 

 higher plants. The groups will be taken in the order 

 of the relative complexity of their reproductive arrange- 

 ments; the simplest forms being treated first and the 

 more complex ones later, particularly as this is con- 

 sidered to be the order of their evolutionary develop- 

 ment. They will be dealt with broadly, and no 

 reference will be made to the characters separating 

 families, genera, or species, as this would prevent the 

 subject from being treated in a sufficiently simple 

 manner. Typical fungi illustrating the characters of 

 any group will be selected as far as possible from those 

 well known in the West Indies, either as causing 

 diseases of crops with which many are acquainted, or 

 as being of some economic usefulness to the planter, 

 for example, the fungus parasites of insects. 



Before turning to tlie fungi tliera.selves, it may be of 

 assistance if some idea is given of what is understood by the 

 words specie.s, genera, natural order and cohort. 



The starting point for all systems of classification of 

 any description of objects is always the individual. Thus, 

 among plants, the first thing noticed is always a collection of 

 individuals, each of which differs from the other to a greater 

 or less extent. On further careful examination, it becomes 

 clear that some of these plants resemble each other 

 more than any other of the plants examined. Such 

 a group of plants is known as a Species. It now becomes 

 necessary to consider on what ground this resemblance is 

 based. On looking at one plant, it may become clear that it 

 is somewhat similar to individuals of another kind, in the 

 way that the Hibiscus resembles the cotton plant. The 

 Cjuestion is: In what ways is this similar to the cotton plant ? 

 Careful examination shows that, though the flowers are of 

 a different colour, yet each has the same number of petals, 

 and the other parts of the flower are alike in each, and of the 

 same number in each. Further, both plants are of a bushy 

 habit, although tlte leaves are different. Thus on tlie sum 

 of various characters exhibited by eacli, there are more points 

 of resemblance than of difference, and consequently the 

 plants may be said to be related to one another fairly closely. 

 The resemblance is somewhat similar to that often shown 

 between the different members of the same familj- in the human 

 race. The idea underlying a natural system of classification 

 is to bring together into the same species those plants 



which are related in the same way as the various members 

 of a human family are related, all of whom had the same 

 ancestors. In speaking of human relation.ships, it is often 

 said that the members of a certain family Iiave one, or possibly 

 two, features that are characteristic, as for example the eyes, 

 the mouth, or even the voice. In considering plants, it is 

 often found that two plants whose general apjiearance is 

 very different have flowers and fruits that are very similar. 

 As in observing the relationships of human beings, 

 greater im[)ortance is often attached to similarity of eyes and 

 voices or any two similar features than to the numerous 

 dissimilarities, so in the case of plants greater importance 

 is often attached to similarities in the flowers and fruit than 

 to dis.similarities of general habit. With plants, this 

 may be done without involving much danger of cla.ssing 

 together those which are not really related, for a reason that 

 may be given as follows. The flowers and fruit of a plant 

 are its reproductive organs, and consequently are not engaged 

 in obtaining food for the plant. Now, while the conditions 

 of tempei ature, moisture, food supply and .so on, under which 

 a plant lives, may have a very considerable effect on those 

 [larts that are concerned with obtaining its food, they 

 will not have so immediate an efl'ect on its reproductive 

 organs. 



Consequentl}', plants which are fairly closely related may 

 show very considerable differences in their vegetative parts, 

 that is in the parts engaged in obtaining their food, while 

 they still exhibit a very close resemblance in their reproduc- 

 tive parts. As a result of this, the classification of all plants 

 rests mainly on the characters of those organs by which they 

 reproduce themselves. 



To return to the definition of species, it is now evident 

 that a group of plants which resemble one another more 

 closely in the sum of their characters, more especially those of 

 their reproductive organs, more than any one of them 

 resembles any other plant in these characters, may be said 

 to form a species. 



Similarly, any group of species, each of which resembles 

 the others more closely than it does any other species, forms 

 a Genus; and similar groups of genera form a Natural Order 

 or Family. Groups of similar families form Cohorts, which 

 are the main subdivisions of the great ])rimary divisions of 

 the jilant kingdom. 



In the case of the fungi, just as has been shown for 

 flowering plants, the characters of the reproductive organs 

 are those on which the classification is most especially based, 

 as in many cases the mycelia, or vegetative parts, even of 

 widely ditt'erent groups, are so similar as to be almost indis- 

 tinguishable. 



Broadly speaking, there are two different types of repro- 

 duction in the fungi. In the first, a special portion of the 

 plant body is prefiared and separated oft" for the purpose of 

 increasing the numbers of the plant. Such a portion is known 

 as a conidium, or spore, and is capable of germinating again 

 very quickly, if it is placed under conditions suitable to the 

 growth of the fungus, such as a sufficient and acceptable food 

 supply, plenty of moisture and a suitable temperature. Such 

 spores are merely i)arts of the plants from which they were 

 cut off, and the plants that grow from them resemble the 

 parent in all respects. As has been pointed out before, these 

 spores are produced in immense quantities when all the 

 external conditions are suitable to the fungus, and are those 

 to which an epidemic of any disease is due. Fungi belonging 

 to very ditt'erent species, or even genera, may produce spores 

 of this kind, which are very similar in appearance, conse- 

 quently such s[iores are mainly of .secondary importance in 

 classification. 



