186 



Mycologia 



cork cells have been pushed up, crushed in or broken down. This 

 disorganization may not be entirely due to pressure. The fungus 

 evidently brings about some chemical changes in the suberized 

 cells. After the buffer cells have lost their contents the cells 

 below bud out, their nuclei move up to the base of the buds and 

 divide. There are now two nuclei in the bud and two in the 

 basal cell. A septum is formed at once. The young binucleated 

 teleutospore bud grows comparatively slowly so that these stages 

 are fairly abundant at the center of the young sorus (PI. 9, Fig. 

 3). Buds may push out of the side of a basal cell (PL 9, Fig. 2) 

 and later three or four buds may be formed from one cell. The 

 cork layer is lifted up and broken open first at the central part of 

 the pit. Mature spores are present when this slight swelling or 

 blistering is first noticeable (PL 9, Fig. 4). The cells of the lower 

 •portion of the stromatic mass do not stain very readily, so that 

 their nuclei do not appear distinctly. Reed and Crabill's diagram 

 (1. c.j Fig. 7) of a sorus, while it perhaps exaggerates somewhat, 

 brings out the point that the spores push up rapidly from a region 

 in the center of the depression, and further development peripher- 

 ally is considerably retarded. The size of the papilla at the center 

 of a depression in the gall determines roughly the diameter of the 

 sorus as it emerges. At the center of the blister the cork cells, 

 especially the innermost cells, are considerably disorganized and 

 crushed in, and nearly mature spores have been formed. Near 

 the margin many long two-nucleated spore buds are present. 

 Buffer cells have disappeared in the whole region beneath the 

 blister, but at its margin and immediately beyond for a short dis- 

 tance a different picture is presented. The cork cells have not 

 been crushed in or lifted up so conspicuously, and buffer cells are 

 plainly visible, fully elongated, and short buds, some without 

 nuclei, are growing up from the basal cells. Figure 4 in plate 9 

 shows a portion of a young sorus at a time when the papilla is 

 plainly visible but before the cork has been ruptured. The con- 

 ditions near the margin of the blister are shown at the right in 

 the figure. The sorus primordium ends rather abruptly just be- 

 yond. The diameter of the raised portion is about one half of 

 the entire depression in this section. Figures 1 to 4 show the 



