314 JOUKNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



ascospores were used under the same method of culture, and in which the 

 same infection results were obtained. 



Further experiments are then recorded in which leaves were injured 

 and thereby rendered susceptible to the attacks of conidia and ascospores 

 which are unable to infect the leaves when uninjured. The injuries 

 inflicted were produced by stabbing the leaf, stamping out minute portions, 

 by pressure with weights, and by the action of heat or narcotics. It is 

 pointed out that injuries similar to those artificially produced in the 

 experiments must be constantly inflicted on plants in nature, by animals, 

 frost, wind, and hail. An example is also given of barley leaves rendered 

 susceptible by the agricultural operation of rolling seedlirg corn. 



In order to account for the susceptibility shown by injured leaves, the 

 assumption is made that, in consequence of the "vitality" of the leaf- 

 cells being affected, the protection normally afforded by enzymes, or 

 similar substances, ceases. The loss of immunity brought about by 

 causes which affect the vitality of the leaf find their parallel in the 

 recorded instances of induced susceptibility in animals to certain diseases 

 caused by bacteria. 



The main results obtained are summarised as follows : (1) Sus- 

 ceptibility can be induced not only by various kinds of mechanical 

 injury, but also by such interference with the normal functions of the cell 

 as follows the application of anaesthetics and heat. (2) The conidia of 

 the first generation produced on leaves of a strange host-plant, previously 

 subjected to action of alcohol, ether, or heat, retain the power of infecting 

 their original host, but do not acquire the power of infecting normal leaves 

 of their temporary host. 



A detailed account of the experiments is given in the latter half of the 

 paper. — A. D. C. 



Erysiphe Graminis DC. under Cultural Conditions, On Endo- 

 phytic Adaptation shown by. By E. S. Salmon (Ann. Bot. xix. 

 July 1905, pp.'444-446).— The full paper on endophytic adaptations of the 

 grass mildew (Erysiphe Graminis) will be found in ' Trans. Roy. Soc. B,' 

 vol. cxcviii. 1905, p. 87. An abstract only is given in Ann. Bot. July 

 1905. 



The author has previously pointed out that certain species of the 

 Erysiphacecs are able, under cultural conditions, to infect their host-plants 

 vigorously when their conidia or ascospores are sown on the cells of the 

 internal tissues exposed by means of a wound, although the fungi in ques- 

 tion are confined normally to the external surface of the epidermal cells. 



The present paper deals with the question of the details of growth of 

 the fungus under these abnormal conditions, and of the extent to which 

 the hypha? penetrate into the intercellular spaces of the internal tissues, 

 and whether haustoria were produced by these hyphae. 



With the'exception of PJujllactinia, the species of the Erysiphacece, 

 so far as they have been investigated, have been found to be strictly 

 ectoparasitic in habit, the hyphae of the mycelium being confined to the 

 external surface of the epidermal cells, and merely sending haustoria 

 either into the epidermal cells alone, or, in the case of one species, into 

 the sub-epidermal cells as well. 



