J. SAUNDERS — WITCHES BROOMS. 



11 



ducts in tlie mesophyll are degraded, and they do not show the 

 usual ring of small thin-walled cells by which they should be 

 surrounded. The hypodermal cells are interinipted at interval^ 

 by the stomata, and here in a number of instances the mycelium 

 is knotted and twisted as if it were thrusting its way through, 

 and possibly during the proper season conidia were liberated 

 from the protruding hyphse." Tubeuf says: " ^cidium cortiscans 

 forms malformed shoots in spruce. In Russia and Scandinavia 

 yEcidiu7n abietinum does not appear to cause witch brooms." 

 Kerner says : " Witches' brooms also occur on pines, larches, 

 and spruce firs, etc., although hitherto we have not been able to 

 ascertain definitely what parasitic fungi are the causes in these 

 cases." 



Silver Fir (Abies jjecthiata). — Witches' Brooms on silver fir 

 are not uncommon in North Norfolk on sandy soil. An account 

 of this, by Mr. W. H. Burrell, appears in the ' Transactions 

 of the Norfolk and Norwich Naturalists' Society,' vol. vii. 

 Although no i*ecords of similar growths in this district are 

 known to the writer, yet it is highly probalile that they would 

 be found if sought over the Lower G-reensand area. In the case 

 of the silver fir the disease is due to the presence of one of the 

 Uredinae, jEcidium elatiniim. The foliage of the brooms is 

 deciduous, whilst the leaves of the normal shoots persist for 

 several years. 



Niunerous records were made during 1904 as to the relative 

 unfolding and fading of the leaves on Witches' Brooms, and of 

 the normal l^ranches of the trees which bear them. 



From lengthened observations by Mr. Gr. Pkunmer, it appears 

 that in the case of the birch on his grounds the leaves of the 

 brooms both unfold and wither earlier than on the other portions 

 of the tree. 



In field elm, wych elm, hornbeam, hazel, and hawthorn, so far 

 as coiild be judged in the springtimes of 1904, 1905, and 1906, 

 the development of the foliage on the brooms and on the healthy 

 portions of the trees was simultaneous, but in' all cases the 

 withering of the leaves was earlier on the brooms than on the 

 normal branches. 



The local effects of the exciting causes of the brooms are 

 manifested in the crumpling of the leaves, their smaller size, 

 usually also their more brilliant coloui'ing, and the atrophy of 

 the twigs. The general effects are an acceleration of development, 

 accompanied by diminished vitality, which results in a shortening 

 of the lives of the parts affected, and in extreme cases of the life 

 of the whole organism. Fruit is also usually absent. 



Dr. W. Gr. Smith informs me that a theory has been advanced 

 by Dr. Kiegenhagen, which assumes that the primordial type of 

 a genus of trees possessed (or was possessed by) its special 

 parasite, and that in the course of subsequent evolutionary 

 changes both host and parasite became specialized along parallel 

 lines. 



