Oct., 1904.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



233 



spores, each spore being divided liy a cross-wall into 

 two equal portions, and supported on a \ cry lon.i^ 

 slender stalk. The mycelium of this condition of the 

 fungus is perennial ; that is, it remains living in the 

 infected jimiper branch from vear to year; consi'qucntly, 

 when a branch is once infected, the disease continues 

 to spread, the swelling continues to increase in size, 

 and a crop of spores is formed every spring. If the 

 orange masses of spores are carefully observed they 

 will be seen eventually to become covered with a 

 delicate whitish bloom, resembling in" appearance the 

 bloom on a plum or a grape. Examination under the 

 microscope shows that this apparent bloom consists in 

 reality of a mass of exceedingly minute spores, or, as 

 they are usually called, secondary-spores, produced by 

 the much larger prexiouslv formed orange spores. 



These secondary-spores, which are produced in 

 enormous quantities, become free when mature, and 

 are distributed by wind, birds, insects, &c., and those 

 that happen to alight on the moist surface of young 

 leaves of pear trees, or on the voung shoots, Ic.ives, or 

 fruit of the hawthorn, germinate and enter the tissues 

 of the living plant, and in course of time produce the 

 second form of fruit, at one time considered as an 

 independent fungus, and called Rocsieliti. The spores 

 of this form are in turn dispersed b}' wind, &'c., and 

 those that alight on a juniper branch give origin 

 eventually to the form of fruit found only on juniper. 



The feature to remember in the abo\e account is the 

 fact that the spores produced by the form of the fungus 

 growing on juniper cannot directly infect a juniper 

 again, but can only infect pear or h;iwthorn ; on the 

 other hand the spores produced on pear or hawthorn 

 cannot directly infect either of these pl.ints, but only a 

 juniper plant. The spores cannot infect any other 

 plant except the three mentioned. 



The very injurious rust of wheat, Puccinia graminis, 

 which abounds wherever this cereal is cultivated, is a 

 fungus having four different forms or phases included 

 in its life-cycle. Two of these appear in the spring on 

 the young leaves of the common barberry, and less 

 frequently also on the fruit of this shrub. The first 

 condition to appear on the leaves, under the form of 

 minute, inconspicuous yellowish clusters of pimples, are 

 the spermogonia, structures of unknown functions, and 

 by some considered as aborted male organs. These 

 are quickly followed on the opposite side of the leaf by 

 clusters of minute, cup-shaped bodies with notched 

 edges, and filled with myriads of very minute golden 

 spores. The last mentioned stage of the fungus was 

 once considered to be an independent plant, and was 

 named Aecidinm bcrheridis. It is popularly known as 

 " cluster-cups," and is a very beautiful object when 

 examined with a pocket-lens, or under a low power of 

 the microscope. The spores produced in the cups are 

 scattered by wind or carried by various insects or 

 animals, and those that happen to alight on the voung 

 leaves of \vheat soon germinate and enter the tissues 

 of the ^vheat leaf, and after the space of a few days 

 rustv-orange streaks appear bursting through to the 

 surface of the leaf. These rusty streaks consist of 

 masses of spores belonging to the third condition of 

 the fungus, once called Vrcdn liueavis. The spores of 

 this form are produced in immense numbers and in 

 rapid succession throuirhout the summer months, and, 

 being scattered by the various atrents enumerated 

 above, it can be readily understood how quickly an 

 epidemic of rust can spread when a few wheat plants 

 in a field have once been infected. 



During the autumn when the wheat is approaching 

 ni.ituritv, the devcloiiment of UrcJo spores ci-ases, and 

 a fourth form of spore, the last in the sequence of 

 (lexelopmcnt, appears on the Icaxi's of the wheat plant. 

 This is the Puccinia stage. These spores remain in a 

 dormant condition until the following sjiring, when 

 thev germinate .and produce \crv minute secondary- 

 spores which, w lien pl.iicd 011 a barberry leaf, give 

 origin again to the s[n'nnoi;oiii.i ,ind " cluslcr-cup " 

 conditions, and the cycle of dcvclopnienl commences 

 anew. 



The " .Smuts " and " Hunts " are also very de- 

 structive to cereals, forming a dense mass of black 

 soot-like spores in the cars. Some species infesting 

 wheat ha\e a very unpleasant odour resembling de- 

 caying fish when rubbed between the fingers. The 

 life-historv of the .Smuts (Ui/ilago) is peculiar. 



The minute bku-k spores are scattered by wind, and 

 remain in tlie soil unlil the following spring, when 

 they giM-minate, and the t;erm-tui3cs enter the tissues 





'v»Jl^ 



rheconidial or first .stase of u fundus called sV/irnfiiim friirliiti-na, very 

 ciimmon on tile fruit of the apple, pear, plum, cherry, &c. It 

 causes tlie fruit to become dry and "mummified" (natural size). 



of seedling cen'.iK. The fungus grows in the tis.sues 

 of the host-plant without doing any apparent injury 

 until the ear is formed, when the fungus develops in 

 the position normally occupied by the grain, and in 

 due time its mass of black, powdery spores bursts 

 through the tissues of its hosl-planl. In all cereals 

 except maize the fungus can only infect the plant 

 during the seedling stage. When a month old the 

 fungus mycelium can no longer enter the tissues. 

 Space prevents more than a passing allusion to the 

 numerous diseases caused by fungi to forest and fruit 

 trees. Larch trees, especially when grown in low 

 damp districts, suffer severely from a small and very 

 beautiful cup-shaped fungus, orange inside, _ snow- 

 white and minutely woolly on the outside. Fruit trees, 

 more especially apple, arc too often killed by a fungus 

 which destroys the bark and produces a cankered ap- 

 pearance, finally killing the branch attacked. 



Neither are fruits exempt, the numerous _ blotches 

 and rotten patches on ripe fruit being in most instances 

 attributable to fungi. 



