400 Harper.—Sexual Reproduction in Pyronema . 
* 
Figs. 16, 16 a, and 1 6 b. Parts of tangential sections of the central mass of nuclei 
in different oogonia showing groups of fusing nuclei in various stages. 1 6 a slightly 
less magnified. 
PLATE XX. 
Figs. 17 a and 17 b. Two sections from the same oogonium showing the separa¬ 
tion of the nuclei after fertilization. Young ascogenous hyphae containing nuclei. 
Basal wall of trichogyne again present. 
Fig. 18. Approximately horizontal section through a rosette of sexual cells 
showing distribution of vegetative branches which are to form hypothecium. One 
of the antheridia does not appear in this section. 
Fig. 19. Section of older oogonium showing the distribution of the ascogenous 
hyphae among the young hyphae of the hypothecium. 
Fig. 20. Section of an ascocarp showing, approximately, the hymenium and 
hypothecium developed from a single pair of sexual cells, a. Portion of ascogenous 
hypha containing unfertilized supernumerary nuclei. 
Fig. 21. Old oogonium with branching trichogyne, which has united with two 
separate antheridia. 
Fig. 22. Oogonium older than that in Fig. 20 and showing large fertilized and 
smaller unfertilized supernumerary nuclei. 
Fig. 23. Semi-diagrammatic drawing of a section of an ascocarp in which the 
first asci are ripening. 
Fig. 24. Storage cells from the hypothecium out of which paraphyses are 
developed. 
Figs. 25, 26. Tips of ascogenous hyphae, from the hymenium, showing pairs of 
nuclei in division. 
* PLATE XXL 
Figs. 27-29. Tips of ascogenous hyphae showing pairs of nuclei in division. 
Fig. 30. Tip of ascogenous hypha showing four nuclei formed by the division 
of the two nuclei shown in preceding figures. 
Fig. 31. Later stage than that in Fig. 30. Dome-shaped young ascus containing 
two nuclei. A second ascus forming below. 
Fig. 32. Slightly older ascus showing two nuclei and two supporting cells. 
Fig. 32 a. Same stage showing a single supporting cell. 
Fig. 33. Nuclei in young ascus fusing. 
Fig. 34. Young ascus with single nucleus formed by fusion of the two nuclei 
shown in preceding stage. 
Fig. 35. Primary ascus nucleus in division. 
Fig. 36. Two young daughter-nuclei formed by division of primary ascus 
nucleus. 
Fig* 37* Division of the secondary ascus nuclei. 
Fig. 38. Dispirem stage of same division. 
Fig. 39. Four-nucleated stage in development of ascus. 
Fig. 40. Eight-nucleated stage. Nuclei with beaks and asters at the tips of the 
beaks. 
P ig. 41. Stage in the cutting out of the ascospores by the folding back and fusion 
of the rays of the aster. 
Fig. 42. Young ascospores enclosed only by plasma-membranes. 
Fig* 43* Nearly ripe ascospores with fungus-cellulose wall. 
