330 XXIV. REPRODUCTION OF THE HIGHER FUNGI AND LICHENS. 



into the ascus-nucleus, which then, by successive bipartitions, 

 gives rise to the eight spore-nuclei. 



Puccinia graminis. In the months of May and June may 

 perhaps be found upon the under side of the leaves of the Bar- 

 berry l (Berber is vulgaris) orange-coloured warts, which, to the 

 naked eye, appear finely pitted. Examination with a lens shows 

 them as cushion-like yellow swellings, upon which are placed 

 small orange-red cuplets. The corresponding positions on the 

 upper side of the leaf appear as reddish spots edged with yellow. 

 Examined with a lens, usually numerous brown dots, surrounded 

 with orange-red, show in the inner parts of them. Individual 

 similar dots are often to be found on the edges of the cushion on 

 the under side of the leaf. The cuplets on the cushion of the 

 under side of the leaf are the aecidi urn-fruits of ^Ecidium Ber- 

 beridis, the " cluster-cup " of the Barberry; the corresponding 

 dots on the spots on the upper side of the leaf, and also upon the 

 edges of the cushion on the under side of the leaf, are the sper- 

 mogqnes appertaining to them. Together they form the first 

 generation of the common fungus, Eust of wheat, etc. (Puccinia 

 graminis), belonging to the >4Ecidiomycetes or Uredineae, of 

 which the second generation is passed through upon our corn and 

 other grasses, giving rise to the appearance of the disease called 

 4 'rust". 



By means .of elder-pith we prepare delicate cross-sections 

 through an infected leaf, and examine them with a low, and 

 afterwards with a high power. We assume that fresh material 

 stands at our disposal ; the investigation can, however, be carried 

 on satisfactorily upon dried and soaked, and very well upon 

 alcohol material. The sections prepared from the fresh leaf are 

 especially clear if we run in a little potash solution. In the 

 uninfected parts the barberry leaf shows, proceeding from above 

 downwards : an upper epidermis ; a single layer of elongated 

 palisade-cells ; a loose spongy parenchyma, about five cells 

 deep ; the under epidermis. The cushions of tissue of the 

 infected parts have attained more than double the thickness 

 of the leaf. Upon the palisade layer of the upper side, which is 

 higher, but otherwise appears little changed, impinges a closed 



1 This plant is now rare in many parts of Britain in the wild state, having 

 been exterminated by farmers for reasons which the life history of Puccinia 

 will render obvious. The commonest ^Ecidiomycete is probably that which 

 forms the rounded yellow swollen patches on the leaves of the Coltsfoot. [Eo.] 



