Spermogonia and the so-called Spermatia. ' "? 



J 



visited this plant. Tulasne * remarked the odour of the 

 spermogonia of yEcidiiiin pini and of Uredo serratulce, 

 which he compared to that of the pollen of willows. 

 Leveille -f* noticed the odour of ^cidiiim tragopogonis, 

 which he said resembled the perfume of some flower. 

 Rathay indicates that the possession of the pleasant odours 

 is a special characteristic of those Uredines which have a 

 perennial mycelium. The plants thus invaded are further 

 rendered more conspicuous to insects by the manner in 

 which the affected leaves or shoots grow. As he says, these 

 have a strong negative geotropism. Not only are they 

 more erect, standing above the other leaves or shoots, but 

 they are further characterized by an alteration in their 

 foliage ; while they are, as a rule, not only paler in colour, 

 but also modified in form, being either more attenuated or 

 the reverse. The Uredines with a short-lived mycelium, on 

 the contrary, have their spermogonia produced upon the 

 upper surface of the leaves on brilliantly coloured spots, 

 which contrast more or less strikingly with the green colour 

 of the healthy foliage. These spots are generally bright 

 yellow or orange, often with a tinge of red. Sometimes 

 they are white {^c. fabcB) or purple-red {^c. rnmicis). 

 The negative geotropism is not, however, confined to the 

 species with the perennial mycelium ; I have noticed it 

 very markedly with some leaves of Senecio jacobcea, upon 

 which I had produced the aecidium oi Piiccinia schceleriana ; 

 as soon as the aecidial spots became sufficiently developed 

 to produce spermogonia, the leaves which bore them became 

 almost erect, while the unaffected leaves remained horizontal. 

 In either case the darker paraphyses surmounting each 

 conceptacle finally attract the insect to the sugary globule. 



* Tulasne, " 2« Memoire," p. Ii8. 



t Leveille, in D'Orbigny's " Diet. Univ. d'Hist. Nat.," tome xii. p. 175, 

 sub. Uredines. 



