_Series IV._ =PORPHYRO´SPORÆ= (Pratelli). _Gr_—purple. Spores typically black-purple or brownish-purple, more rarely dusky brown. (It is to be observed that the spores vary in color according to the color of the ground on which they are deposited.) There are sterile forms with the gills persistently white (A. obturatus, A. udus). Those species are more deceptive in which the gills continue for a long time white, and even begin to decay before they are discolored by the spores; these may be easily mistaken for Leucospori. _Fries._ Pratelli is the name given by the early authors to this series, based upon the spore color; Porphyrosporæ is the name now used. The species within the group are closely allied to those having black spores without a tinge of purple or violet (Melanosporæ), but in none of the species do the gills deliquesce as in Coprinus, neither are there resupinate or lateral stemmed species. There is a present tendency to do away with this series and include all dark-spored species in the Melanosporæ. Professor Atkinson and Bertha Stoneman, in their “Provisional Key to the Genera of Hymenomycetes,” omit the series and give “Melanosporæ, Gill and Butz (Pratellæ and Coprinariæ in broadest sense). Spores dark brown, purplish-brown or black.” [Illustration: PORPHYROSPORAE. _Hymenophore distinct from fleshy stem._ PILOSACE. AGARICUS. (PSALLIOTA.) CHITONIA. _Hymenophore confluent and homogeneous with fleshy stem._ STROPHARIA. HYPHOLOMA. _Hymenophore confluent with, but heterogeneous from cartilaginous stem._ PSILOCYBE. PSATHYRA. DECONICA. PLATE XCII. CHART OF GENERA IN PURPLE-SPORED SERIES—PORPHYROSPORAE, PAGE 330. ] (Plate XCIII.) [Illustration: CHITONIA RUBRICEPS. Two-thirds natural size. ] It is frequently difficult to determine by the spore-color of this series even to which series a specimen belongs. Many of our best edibles belong in this series. I know of none noxious. =CHITON´IA= Fr. Universal veil distinct from the pileus, at maturity forming a distinct volva round the base of the ringless central stem. =Gills= free from the stem. =Spores= brownish-purple. Analogous in structure with Volvaria and Amanitopsis. An exotic genus imported into this country. No American species reported. [Illustration: Grouped by F.D. Briscoe—Studies by C. McIlvaine. PLATE XCI.] FIG. PAGE. FIG. PAGE. 1. AGARICUS VARIABILIS, 346 4. AGARICUS CAMPESTER, 332 2. AGARICUS SILVICOLA, 343 5. AGARICUS CAMPESTER 332 (SECTION), 3. AGARICUS PLACOMYCES, 345 AGAR´ICUS.