NATURAL HISTORY SOCIETY OF GLASGOW. 297 



by a stem to the tissues of the host-plant, as they are not meant to 

 be thrown off and to germinate immediately like the rust ones. 

 They lie quiet for months awaiting springtime. Then they germin- 

 ate, sending out a filament from each of their two divisions. The 

 upper part of this filament gives off three simple tapering branches, 

 each bearing a clear yellowish spore-like body at the tip. Off on 

 the wind float these sporidia, and some at last reach a haven of rest 

 on a barberry bush. Falling on a leaf they do not take the trouble 

 to hunt out a stoma, but bore right through into the interior, where 

 they send out mycelial threads, and in about a week cluster-cups 

 are produced. The cluster-cup spores will not — so far as known — 

 germinate on the barberry, nor will these clear yellow spores on 

 grasses. In the barberry seems to lie for this parasite as a species 

 the secret of renewed possibilities of vigorous mischief. There it 

 would appear to touch afresh the torch of life, and through 

 mysterious sexuality — as I have already remarked, a sexuality as 

 yet only surmised — to develop latent force. The youthful spore 

 is thrown off full of vital zeal, and its fresh vigour infuses itself 

 into the threadlets of destruction which it sends into the grasses. 

 Bust and mildew may perhaps be able to propagate themselves for 

 years in some milder makeshift way without fresh cluster-cups ; but, 

 when the spores from such cluster-cups come, ruin comes with them. 

 They set to with a will, and the wheat stalk often dies green, and 

 rarely produces more in the shape of grains than shrivelled starve- 

 lings. We can then say with Shakespeare — 



' ' The green corn 

 Hath rotted ere his youth attained a beard." * 



Many other instances illustrative of hetercecism may be adduced. 

 The cylindrical peridia ( Peridermium Pint) that sometimes occur 

 on the young leaves of Scotch Fir send out spores that are said to 

 produce the golden rust ( Coleosporium Senecionis) on the under side 

 of groundsel leaves. The tufts of minute tassels (Rmstdia lacerata) 

 on the leaves and fruit of the hawthorn are a phase in the life of 

 the parasite on the common juniper (Podisuma Juniperi); those 

 on pear leaves (Roestelia cancellataj, of the parasite of Savin 



* Further details on this interesting subject will be found in the various 

 papers by de Bary, and in his book, " Neue TJntersuchungen liber Uredineen," 

 Berlin, 1865; in the English translation of Sachs' "Textbook of Botany," 

 2nd Edition, page 330; and in " Grevillea," "The Gardener's Chronicle," 

 " Science Gossip," and other English serials for 1881, and since. 



