368 DIVISION III. MODE OF LIFE OF THE FUNGI. 



Carbo, Claviceps, and many others) belong to the same category, together with all 

 those that live on animals, unless we choose to reckon the phenomena of inflammation, 

 suppuration, and formation of tumours caused by the presence of the Fungus 

 in warm-blooded animals as cases of abnormal growth, a point which may for 

 the present remain undecided. 



The occupation by the deforming parasite is followed immediately by anomalous 

 processes of growth in the host or in the parts of the host, the word anomalous being 

 here understood to mean every condition different from that which is found in the 

 plants or the parts not attacked by the Fungus. Countless examples of this class of 

 parasites are to be found among those which live on plants. The phenomenon 

 necessarily presupposes a power of growth in the parts to be deformed, and in the 

 higher plants therefore it usually implies that they were attacked in the young state 

 when their growth is still incomplete. 



The extremes of deformation, which pass, it is true, readily into one another, consist 

 on the one hand in an abnormal increase of growth and abnormal enlargement of parts of 

 the tissue, which are in other respects normal and normally disposed, and hence in the 

 swelling of the individual cells, as in the case of epidermal cells which are occupied by 

 Synchytrium and the adjoining cells, or else in a monstrous enlargement and inflation of 

 .entire members and aggregates of members in the higher plants, such as the swelling of 

 the flower-stalks and the enlargement, often to an enormous size, of the flowers of the 

 Cruciferae when attacked by Cystopus. These may be said to be cases of hypertrophy. 

 On the other hand the parts may be deformed with very slight or with no hypertrophy 

 worth mentioning ; such are well-known deformations of the shoots of herbaceous 

 species of Euphorbia by Uromyces Pisi, U. scutellatus, and Endophyllium Euphorbiae, 

 and the 'witches' brooms ' on the branches of the fir and cherry-tree when attacked by 

 Peridermium elatinum or Exoascus. In the fir (Abies pectinata), for example, these 

 branches grow vertically upwards, like small trees, from the horizontal limbs, with 

 branches spreading in every direction, and leaves which spread in the same manner and 

 fall off year by year, while the entire excrescence continues to grow for years l . In the 

 flowers of Knautia arvensis, when occupied by Peronospora violacea, the stamens often, 

 though not always, acquire the characters of normal petals of a beautiful violet colour, 

 and the blooms are filled by them. These phenomena of deformation by Fungi may 

 be termed mycetogcnetic metamorphosis. The processes in the formation of Lichens, to 

 which we shall recur in a later page, have a considerable resemblance to them. 



Lastly, the new formation of members, such as are not seen in any form on the 

 plant when free from the Fungus, are caused on parts of some of the higher plants by 

 the presence of the Fungus. The most striking instances of the kind are the delicate 

 round bodies of the size of a cherry which Exobasidium Vaccinii produces on the 

 leaves of the alpine rose, and the excrescences on the stem of Laurus canariensis, L. 

 caused by Exobasidium Lauri and described at length by Geyler 2 , club-shaped for- 

 mations with blunt edges, of the length of a finger, and branched like an antler, 

 which Schacht even mistook for aerial roots. But the strangest example of the kind 

 is found in the Saprolegnieae when attacked by Rozella, which will be described below. 



Bot. Ztg. 1867, p. 257. 

 Bot. Ztg. 1874, p. 321. 



