lU 



NOMAU FUNGI. 



But, later ou iu the year, we find, on the leaves of the same plant 

 a fungus of a very different character. There is no cup, no chains of 

 spores ; the spores are collected in loose rounded heaps, resembling 

 the sori of ferns, apparently resting lightly on the epidermis of the 

 leaf, not usually combined in clusters, but scattered over the surface. 

 Instead of the beautiful white fringe which surrounds the CEcidiuni, 

 we have here merely the ragged edge of the ruptured epidermis, 

 showing that the fungus originated just beneath the epidermis, and in 

 its growth burst it open. The oval spores are brownish, and each is 

 formed singly by a constriction of the end of a hypha, but otherwise 

 they are very similar to those of the CEcidium. This fungus used to 

 be known as Trichobasis or Uredo violarum. 



At the same time, or later, we can find on the same leaves still 

 another fungus of a different kind. In this case the spores grow, as 

 in the Uredo, from the ends of the branches of the hyphae, and 

 frequently, if not always, from the same mycelium which has hitherto 

 produced the Uredo-spores. The sori are surrounded, iu the same 

 way, only by the ruptured epidermis. But the spores are very 

 different in character. While the Uredo-spores are easily detached 

 from their support, these often remain firmly fixed to the 

 byphu from which they originated, which breaks oif with them as 

 a kind of stalk ; each spore consists of two cells, separated by a 

 transverse XDartition, or rather two spores are produced on each hypha, 

 for each cell of the compound spore is capable of independent germina- 

 tion. The greatest difference of all is, however, in the cuticle of the 

 spore, which iu these is greatly thickened and strengthened, in the 

 same way as the outer surface of the epidermal cells of many leaves 

 is cuticularised, iu order to enable it the better to resist the attacks 

 of the weather. This last form of fungus is called a Puccinia, and 

 our species is known as Puccinia violanan. 



Now undoubtedly the first impulse of the student, on seeing these 

 various kinds of fungi, would be to class them as three distinct species, 

 belonging to thi'ee distinct genera, and placed respectively in the three 

 orders which have been mentioned above. But this impulse, though 

 natural, could not stand the test of a more careful examination. Our 

 student would find the same sequence of phenomena on other species 

 of plants. The common Epilobiums would provide him with three 

 fungi, successively making their appearance on the leaves, in the same 

 way and in the same order, viz., (Eciditim epilobii, Tricliohasis epilobii, 

 and Puccinia pulverulentu. The species of Allium, of Prinaula, of 

 Mentha, of Galium, of Sanicula, and many others, all tell the sarue tale. 

 This should have awakened suspicion, but at first apparently did not. 

 Moreover, the Uredo and Puccinia-forms appear, as I have said, often ou 

 the same leaves at the same time, and are obviously seen to spring from 

 the same mycelium, not only iu the species which I have mentioned, 

 but in very many others. This fact, when fuUy brought to light, was 

 so far conclusive ; and the phenomenon was known under the name of 

 Dimorphism. Those who have read Mr. Cooke's useful little book ou 



