On the Biology of Paniis stypticiis. M. E. M. Johnson. 349 



was continually absorbing moisture. The cultures were placed 

 in sets of three in large sterilised closed glass vessels. In about 

 12 days mycelium appeared wliich grew especially well on silver 

 birch. After 5 weeks' growth, the cultures were removed to 

 larger vessels and placed luider similar conditions of light and 

 moisture. Growth was then more rapid and within three weeks 

 young sporophores appeared. Bayliss* also observed that an 

 increased supj:)ly of air had a beneficial effect upon wood block 

 cultures of PolysticHts versicolor and this was followed by the 

 production of small sporophores, but since then she obtained in 

 less than eight months well develoi)ed sporophores of Polysticltts 

 versicolor-f by using large instead of small sterile blocks of wood 

 kept under good conditions of aeration and humidity. 



Oidia were observed only in hanging drop cultures. 



Destruction of Wood. The growth of the mycelial strands, 

 which interlace in the vessels, wood fibres and medullary rays, 

 causes the wood to become light, very soft and paler in colour. 



Sections showed that the more highly lignified elements per- 

 sisted the longer (fig. i^) while the less lignified spring elements 

 were the first to disappear (fig. la). In some cases the second- 

 ary thickening of the cells is first absorbed, the middle lamella 

 persisting (fig. la) but finally this is removed also. In other 

 cases the hyphae have penetrated straight through a cell wall, 

 the middle lamella having been dissolved at the same time as the 

 other part of the cell wall (fig. la). Sometimes the hyphae pass 

 from tracheid to tracheid via the bordered pits. In the autumn 

 wood and medullary ray cells, the pits become enlarged (fig. ib). 



The Sporophrrc. This first appears as a tiny white knob about 

 Jth of a cu. mm. in size (fig. 2). Within one or two days this 

 tiny white knob grows into a horizontal pyramidal mass about 

 if mm. in height (fig, 2a), increase in elevation being due to 

 elongation of the contained hyphae. Soon a tiny pileus can be 

 recognised (figs. 2h' and 2b), and the stipe lengthens; sometimes 

 the latter is only about i mm, in length when the pileus first 

 appears. The hyphae of the stipe gradually cease to grow ter- 

 minally and then commence to branch, many of the branches 

 following a horizontal direction, giving rise to the pileus. This 

 is indicated by the flattening and broadening out of the apex of 

 the stipe (fig. 46). These horizontal hyphae give off vertical 

 branches which remain more or less parallel, and finally cease 

 to grow, and so give rise to the dorsal tissue of the pileus. Other 

 similar branches are given off which turn downwards and form 

 the hymenium, which can be seen when the pileus is about 

 2| mm. across (figs. 4c, 2c', 2c). The young pileus is globose and 



* Jessie S. Bayliss, The Biology of Polystictus versicolor. Journal of 

 Economic Biology, iii, 1908. t An unpublished statement. 



8—2 



