Figure 2. Mature to nearly mature spores with fully developed intine.

a, b. Serial sections of a nearly mature Phaeoceros carolinianus spores in a tetrad surrounded by spore mother cell (smc) wall. a. Aniline blue fluorescence reveals callose in the intine, aperture (ap) and equatorial girdle (eg). b. DIC serial section of 2a shows aperture (ap) and exine outside of the intine with exine 1 (e1) forming the surface ornamentation of the spore. c, d. Phaeoceros carolinianus mature spore not enclosed in spore mother cell wall. c. Aniline blue fluorescence of intine. d. Intine (in) interior to the exine with outer layer (e1) forming ornamentation. e-i. Immunogold labeling with anticallose antibody in diverse hornwort genera. Only the intine (in) is labeled for callose. No labelling occurs in the outer exine (e1) and inner exine (e2). e. Phaeoceros carolinianus. f. Notothylas orbicularis. g. Leiosporoceros dussii. h. Anthoceros agrestis. i. Megaceros flagellaris. j. The spore wall of Dendroceros crispatus consists of two layers, exine (e) and fibrous intine (in), both of which lack labeling with the anticallose MAb. Bars: a, b = 20μm; c, d = 15μm; g = 100nm; h, j = 500nm; e, i = 250nm.