38 Origin of Spore-forms. 



part in the reproduction of the fungus. Its meaning seems to have been 

 lost, but its origin from the sporidiolum seems to indicate that it may be 

 the survival of the conidial reproduction of the sporidiolum. 



Unless in cases where the mycelium is perennial, the sporidiolum ger- 

 minates and produces a mycelium, which gives rise to the spermogonium. 

 The same mycelium may either produce aecidia, as is usually the case, or 

 in the absence of aecidia, uredospores; or, if both are absent, the teleuto- 

 spores, as in Uromycladium tepperianum. The spermogonia are never pro- 

 duced alone, but always precede or accompany some other spore form, for 

 the very good reason that they are incapable of reproducing the fungus. 

 When the spermogonium is about to be formed, the hyphae become inter- 

 woven, and form a tangled mass in (the sub-epidermal tissues. From this 

 numerous delicate branches are given off, which are directed towards the 

 epidermis. These branches converge towards a central point and form a 

 somewhat round or piriform body, which is only covered by the cuticle at 

 the top. The periphery of this body consists of a dense felted mass of 

 sterile hyphae, quite unlike the peridium of the aecidia, which are likewise 

 always deeper-seated than the spermogonia. The so-called spermatia arise 

 inside the spermogonia in short chains by a process of abstriction at the 

 end of fertile converging hyphae, and are held together by a gelatinous sub- 

 stance which contains a certain amount of saccharine matter. (PI. XXIII., 

 Fig. ^203.) 



The probable origin of this puzzling body may thus be accounted for : 

 We may suppose that the sporidiola were spread principally by wind and 

 rain, and at first only produced teleutospores. But in order to secure the 

 intervention of insects which were now becoming adapted to the floral 

 world, a new kind of reproductive body was developed, and the sper- 

 matia abstricted in chains were produced in spermogonia with a sweet 

 bait to attract insects. But when the teleutospores gradually developed 

 uredospores and the same mycelium could produce the three spore-forms 

 spermatia, teleuto. and uredo spores then the former became less and less 

 necessary. When finally the aecidiospores were developed, produced in gieat 

 abundance, and also in chains, then the competition was too keen, and 

 the necessity for spermatia practically ceased to exist, since the germinat- 

 ing sporidiola could produce the aecidia, and the germinating aecidia both 

 the uredospores and ithe teleutospores. Besides, the bright colour of the uredo 

 and aecidio spores may serve -to attract insects for purposes of distribution, 

 and so they were able completely to replace the- spermatia. Finally, the 

 spermatia lost their capacity for germination, and now the spermogonium is 

 an organ which has survived its function, and only remains as a land- 

 mark to show what once had been the prevailing type of reproductive body 

 adapted for distribution by insect life. 



We can thus picture to ourselves the progenitors of the rusts leading 

 a saprophytic existence and gradually adapting themselves to the new 

 mode of life when the parasitic habit was developed and a modification in 

 the spore-forms occurred. The evidence of this great change is shown in 

 the development of a spore primarily adapted for undergoing a period of 

 from the stored-up material directly producing a basidium with 

 sporidiola, instead of being preceded by a more or less scattered mycelium 

 The peculiarity of the teleutospore lies in the fact that it is an in- 

 pendent body capable of giving rise directly and without any further 

 ood supplv to fresh spores by the production of a septate germ-tube 

 which develops secondary spores unlike the original, being smaller, thin- 

 walled, and ready to germinate at once on the damp surface of a living leaf 

 In course of time the teleutospores became differentiated into forms 

 adapted for extremes of temperature and resting, as well as other forms 



