242 ERGOT (CLAVICEPS) 



more central ones, forming the lighter-coloured region, are laden 

 with food-reserves. The sclerotia drop off in the autumn and 

 remain dormant in the soil until the following spring. Then 

 they send up one or more stalked swelhngs (Fig. 128, D), in 

 which are embedded numerous flask-shaped cavities {peritJiecia, 

 Fig. 128, E, p.) communicating with the exterior by small pores 

 (Fig. 128, F). Each pcrithecium is lined with a hymenium 

 similar to that of Pcziza, but the ascospores developed within 

 the asci are in this case thread-hke (Fig. 128, G), so that they 

 are readily distributed by the wind. If caught by the stigma 

 of a Grass-flower the spores germinate and the hypha grows 

 down through the style into the ovary, thus bringing about a 

 fresh infection. 



By slow degrees the contents of the ovarj' are replaced bj? a 

 dense hyphal mass with deep surface furrows (Fig. 128, B, upper 

 part). From the ends of the superficial hypha;, which are more or 

 less parallel to one another, large numbers of minute oval gonidia 

 are budded off (Fig. 128, C), and at the same time the surface 

 secretes a sugary liquid. This attracts insects, to whose bodies the 

 gonidia adhere, and so a rapid spread of the disease from flower 

 to flower is brought about. Later in the summer the production 

 of gonidia ceases and the outer hj'phte blacken, whereby' the 

 resting sclerotium is formed. 



The bright red pustules of Ncdria and the branched sclerotia 

 of the Stag's Horn Fungus (Fig. 126, A) harbour flask-shaped 

 perithecia similar to those of the Ergot. 



In some Ascomycetes reproduction by gonidia is far more 

 frequent than the formation of asci, as, for instance, in the two 

 common Moulds Penicilliitm (Fig. 129, a, h) and Eurotium 

 (Aspergillus, Fig. 129, /). Here the gonidia are budded off in 

 chains from the terminal branchlets of erect h3'phae which, in 

 the case of Eurotium (Fig. 129, /), are strongly swohen at their 

 apices. Both Fungi also occasionally produce spherical ascus- 

 fruits (Fig. 129, d), which arise from special sexual organs 

 (Fig. 129, c), although it is doubtful whether any actual fusion 

 of cell-contents occurs. 



In the White Mildews [Erysiplmcccr) ^ formation of gonidia 



' The Mildews arc the cause of many famiUar diseases of cultivated 

 plants, as instances of wliich may be mentioned the Cooscberry Mildew 



