12 NOTES ON WINTER BOTANY. 
Both insects and the mycelia of the larger fungi generally 
make their attack between the bark and wood. ‘There are the 
cambium of living cells, as well as soft phloem and the youngest 
wood. Having burrowed through and devoured all this material, 
the most usual proceeding is for the fungus to penetrate by the 
medullary rays (also full of starch, vegetable fat, and oil) so as 
to reach towards the pith.* 
Quite frequently the whole wood then becomes a mass of 
thin papery sheets reminding one of the leaves of a book and 
exceedingly thin. A favourite place for Discomycetes is the 
smooth, still hard, surface of the wood covered over by the loose 
shell of bark, and where worms, wood lice, centipedes, slugs, 
small shells, insect larve, etc., find shelter. The shining white 
translucent Lachnella Hyalina often occurs in this position. 
Here also Myxomycete fungi are to be found. The plasmodia 
may be often noticed, and very often the fructifications, though 
these are perhaps more usual where the bark has come off. 
On the other hand, many Spheriaceae grow and feed 
beneath the bark, but, when mature, their little rounded black 
shoulders burst up through the bark and the minute opening is ex- 
posed to the air. Others, such as Nectria, Hypoxylon fuscum, 
and many others, combine to form a circular or lens shaped mass 
(stroma), which breaks up through the bark and so attains the 
air and light ; in these the small pores may be observed, and are 
obviously excellently adapted to the purpose of spore dissemina- 
tion. 
It is as regards the dissemination of the spores of all these 
four groups (Agaricineae, Discomycetes, Sphzriaceae, and 
Myxomycetes), that one finds oneself face to face with difficult 
but most interesting problems. 
How is it that, e.g., Arcyria Punicea occurs on dead wood in 
Britain, France, Germany, Poland, Italy, the Cape, Java and 
Borneo, New Zealand, the United States, the West Indies, 
Guiana, and Brazil?+ Probably that form was differentiated at 
the very origin of the species of trees, and has accompanied trees 
in all their migrations all over the world. More remarkable, 
* ef. Lindroth Naturw. Zeits. f. Land u. Forst. Band II., 1904 (Polyporus 
nigricans) Biffen, Journ. Linn. Soc., April, 1899. 
+ Lister, Mycetozoa. 
