INJURIES INDUCED BY PLANTS 99 



at the base of the ovary, though completely independent of it. 

 Morphologically it is essentially distinct from Sphacelia segetum 

 in having a peculiar pseudo-parenchymatous structure. The 

 original tissues of Sphacelia segetum, with possibly some 

 remnants of the ovary, die completely, and adhere for a short 

 time to the apex of the ergot. 



From what has been said, it will be seen that the disease is 

 spread partly by the sclerotia that hibernate from year to year, 

 and partly by the innumerable gonidia which, suspended in the 

 solution of honey-dew, are carried by various species of insects 

 to the healthy graminaceous flowers where they germinate and 

 which they infect. 



On account of the sclerotia that reach the fields in the seed 

 being still capable of germinating in spring, the farmer en- 

 deavours to prevent the disease by using clean seed-corn. 

 The ergot should also be gathered before harvest, and this 

 is accomplished at little cost, because it fetches a good 

 price.* 



AGLAOSPORA TALEOLA 1 



Amongst the many forms of canker met with on the oak,, 

 some of which still await investigation, the one that is caused 

 by Aglaospora Taleola is characterised by a number of striking 

 peculiarities. It would appear to be confined to woods under 

 the age of forty years, and it is only so long as oaks are without 

 true bark that they are liable to attack. The disease manifests 

 itself in the following way. Both on the dominant and the 

 smaller trees large patches of the smooth cortex die and become 

 brown, but as this usually occurs only on one side of the stem 

 the whole of the tree does not succumb. As the cortex often 

 dies over long distances and on various sides of the tree, patches 

 of sound cortex are to be met with surrounded on all sides by 

 dead tissue (Fig. 46, I, a). A year afterwards numerous round 

 or oval cushion-like stromata appear in the dead cortex. Later 

 on these break through the periderm in one, two, or three places, 

 so as to open up external communication with the gonidiophores 



1 Forstlich-naturivissensch. Zeitschrift, January, 1893. 

 * [Owing to its use in medicine. ED.] 



H 2 



