3'8 



PART IV. VEGETABLE TAXONOMY. 



Fig. 520. 



Fig. 515.— Head of Rye, bearing three Ergot-grains. 



Fig. 516. — Pistil of Rye attacked by Ergot blight — Claviceps purpurea in the first or 

 sphacelial stage of development. Somewhat magnified. 



Fig. 517. — Ergot-grain after lying over winter, producing fructifying organs. Nearly 

 natural size. 



Fig. 518. — A fructifying organ or stroma of Ergot in longitudinal section, magnified. 

 a, a, perithecia imbedded in the margin. 



Fig. 519. — A perithecium much more highly magnified, showing the club-shaped asci in 

 its interior. 



Fig. 520. — One of the asci greatly magnified, shown in the act of discharging its asco- 

 Spores. The discharge really takes place from the ascus, before it leaves the perithecium. 



