206 Transactions of the Society. 



outside forming the cuticle, where, owing to the diffluent walls, the 

 threads are agglutinated together, and form a hard brittle crust when 

 dry. The thick hyphae forming the framework of the pileus also give 

 origin to fine lateral branches, which are at first but little compacted, 

 but eventually become densely felted, and form the cuticle of the pileus. 

 A few small branches, springing from the hyphaa situated on the 

 inside of the thickening ring, form a loose framework in the hollow 

 of the stem; a similar framework originates from the under side of the 

 strengthening rays of the pileus. The structures already described are 

 purely mechanical or protective in function, and consist entirely of 

 very thick-walled, eseptate hyphas. The second or reproductive por- 

 tion, on the contrary, is composed of very thin-walled septate threads, 

 generally copiously branched, forming compact but not hardened masses, 

 except in the hymenium or spore-bearing portion. This latter system 

 occupies the central cavity of the stem within the mechanical ring, 

 from which it extends through the framework between the ribs and 

 the cuticle of the pileus, forming the so-called flesh, then passes down 

 between the ribs and gives origin to the porous hymenium. 



There is no evidence of any organic connection between the hyphae 

 of the two systems, in either stem or pileus; and in all probabihty, 

 differentiation takes place before the plant emerges from its vegetative 

 mycelium. 



Polyporus pisocliapani* has a pileus about three inches across, 

 a central stem about four inches long and more than half an inch 

 thick. Other species of Polyporus in the same collection, in a more 

 or less decayed condition, show a similar differentiation of tissues. 

 P. rugosus Kees has the mechanical sheath of the stem irregularly 

 perforated, while in P. Upideus Fr. and P.jloccopus Eostk., the corre- 

 sponding portion of the pUeus consists of a perforated plate, which 

 sometimes shows a tendency to become broken up into ribs, as in 

 P, insochapani. 



No member of the Agaricini, so far as I have been able to 

 ascertain, shows such a marked division of labour amongst its com- 

 ponent hyphas for purposes of support ; nevertheless, in most species, 

 there is a well marked cuticle to the pileus composed of slender felted 

 hyphae, and the stem generally becomes hollow with age, a firmer 

 peripheral portion remaining, which probably corresponds to the more 

 highly developed mechanical sheath in the stem of Polyp)orus. If 

 however, the supporting hyphae differ but little from those concerned 

 with reproduction in the gill-bearing agarics, we find in some genera, 

 as Lactarius and Bussula, a highly specialized laticiferous tissue, which 

 is distinct from the earlier stage of development. The vessels of this 

 system generally form bundles in the peripheral portion of the stem, 

 from whence they pass into the pileus and gills. In Lactarius two 

 types of structure occur ; the vessels are the result of cell-fusion, only 

 few of the transverse septa remaining, as in L. deliciosus ; f or they 

 consist from the first of eseptate hyphae, much branched and frequently 



* P. pisochapani Nees = P. amhoinensis Fr. ' Grevillea,' xv. (1886) p. 58. 

 t For detailed descriptiun of tlie laticiferous system in tliis fuugus, see Prof. A. 

 Weisd, SB. K. Akad. Wiss. Wien, xci. (1885) pp. 106-202 (i pis.)- 



