320 ATKINSON— MORPHOLOGY AND [April 23, 



viduals may become nearly or quite closed by the increase in the 

 elements of this ground tissue, which forms a portion of the mar- 

 ginal veil, but chiefly by the epinastic growth of the pileus margin 

 which crowds this ground tissue up against the margin of the lam- 

 ellae, as shown in Figs. 32-38. 



Organisation of the Palisade Layer. — The level palisade layer of 

 the hymenophore follows the primordial stage, immediately after 

 the latter stage has become dense and compact by the increase in 

 number and thickness of the parallel hyphal elements. The grow- 

 ing compactness of the primordial hymenophore zone is accom- 

 panied by the evening up of the hyphal ends into a plane surface. 

 As the ends of the hyphse broaden the free surface of the hymeno- 

 phore becomes compact and smooth, or even. This is the level 

 palisade stage of the hymenophore. It is a gradual, not abrupt, 

 transition from the primordial stage. It begins next the stem, or 

 in many cases on the outer surface of the upper part of the stem 

 fundament as shown in Fig. 12. Here the palisade area, in radial 

 section, rises upward at a strong oblique angle from the axis of the 

 stem, and then grades into the primordial area toward the left. 

 The palisade area progresses, like the primordial area and the pileus 

 margin, in a centrifugal direction, the older portion lying next to, or 

 on the upper part of the stem fundament. 



The level palisade layer of the hymenophore, preceding the ori- 

 gin of the lamellae, was first described by Hoffmann^^ in 1856, i860, 

 and 1 86 1, in about a dozen species (see the later paragraph on the 

 origin of the lamellae for a list of species). DeBary^* (i859j P- 3^6, 

 394) described the palisade layer of the young hymenophore in 

 Nyctalis asterophora and parasitica, as having radial folds from its 



13 Hoffmann, H., " Die Pollinarien und Spermatien von Agaricus," Bot. 

 Zeit., 14: 137-148; 153-163, pi. 5, 1856. Beitrage zur Entwickelungsge- 

 schichte und Anatomic der Agaricinen," Bot. Zelt., 18: 389-395 ; 397-404, 

 pis. 13, 14, i860. Icones Analyticae Fungorum ; Abbildungen und 

 Beschreibungen von Pilzen mit besonderer Rucksicht auf Anatomic und Ent- 

 wickclungsgcschichte," 1-105, pis. 1-24, 1861. 



1* DcBary, A., "Zur Kenntnis einer Agaricinen," Bot. Zelt., 17: 385-388; 



393-398; 401-404, pl- 13, 1859- 



i^DeBary; A., "Morphologic und Physiologic dcr Pilze, Flcchten und 

 Myxomyccten," Leipzig, 1866. " Vergleichende Morphologic und Biologic 

 der Pilze, Mycetozoen und Bactericn," 1884. " Comparative Morphology 

 and Biology of the Fungi, Mycetozoa and Bacteria," Oxford, 1887. 



