338 THE BEGINNINGS OF LIFE. 



The two modes of origin of organisms to which we 

 have just alluded may also lead to the presence of 

 ^Bacteria and larger Fungus-germs within the interior of 

 closed cells, both in plants and animals. 



Myriads of microscopic fungi belonging to the pro- 

 tean types included under Rust, Smut, Mildew, and 

 Mould ] , are habitual dwellers in and upon the surfaces 

 of living plants, especially when they are in a sickly 

 condition although others are often found in and upon 

 plants which present no other sign of disease. These 

 particular kmds of fungi are encountered only in such 

 situations, and they recur in similar habitats with 

 tolerably constant forms. The ravages of many of 

 them are matters of no small importance to mankind 

 on account of the very serious damage which they 

 help to produce in our food-supplies. We need only 

 mention the fatal c blights' which they are apt to 

 occasion amongst our cereals, and those devastating 

 diseases of the vine, the hop, and the potato, in which 

 fungi of this kind appear as the most active agents of 

 destruction. The original mode of origin of these 

 various growths is still involved in doubt and obscurity, 



blood, but were capable of flourishing there. Again, Dr. Gros (' Bull, 

 de la Soc. de Nat. de Moscou,' 1845, p. 424) says: ' Le sang d'une 

 mulot nous a presente des vermicules si nombreux que toutes les vesi- 

 cules en avaient 1'air animees. et si petits qu'ils etaient a peine recon- 

 naissables a 400 diametres. Le sang des taupes presente souvent le 

 meme cas.' 



1 See a useful little book by M. C. Cooke, entitled 'Microscopic 

 Fungi,' 2nd ed. 1870. 



