400 



UREDINEAE. 



characteristic of (!. elavariaeforme. Xo mycelium occurred in 

 the wood. A comparison of normal bast with that of infected 

 twigs revealed changes similar to those already described for 

 G. elavariaeforme. In addition, it is to be noted that the 

 thickened bast-fibres no longer occurred in closed masses, but 

 were often completely absent in the first year after infection, 

 while in all diseased twigs every intermediate stage exists 

 between thin-walled bast-elements and thick-walled bast-fibres, 

 such as never occur in the normal twigs ; in fact, many twigs 

 had thin-walled elements only. 



FIG. 235. Swelling from 

 a branch of Junipei-un 

 fyiliiiui attacked by Gymno- 

 :*/iii,'<r,<ijiii ,,i x/iliinae. Dia- 

 meter at thinnest part 1'7 

 centimetre, at the thickest 

 6 c.m. (v. Tubeuf phot.) 



FIG. 236. Sections of a twig of Savin attacked by (1. sabinae. 

 -, At thickest part of the swelling ; ', 3 c.m. under n and normal. 

 In is shown one of the hollow teleutospore-cushions ; five 

 cushion-scars ; in the second-year ring are two shaded zones 

 of wood, chiefly composed of parenchyma, (x 25.) (After 

 Woernle.) 



The sporogenous cushions of G. xabinae are formed in quite 

 a different manner from those of G. elavariaeforme. Beneath 

 each cushion the bast increases very rapidly and forms an out- 

 growth, which is still further enlarged by the addition to its 

 apex of six or seven rows of radially arranged cells, rounder 

 and smaller than the bast-cells of the cushion. The mycelium 

 penetrates between these outer cells, and forms over the whole 

 cellular outgrowth a pseudoparenchyma from which the sporo- 

 genous tissue arises. 



