Inheritance in a Hepatic

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Abstract
No evidences of the occurrence of hermaphroditism or intersex-uality have been observed in Sphaerocarpos donnellii Aust. The 2 spores of each tetrad receiving an X-chromosome, if they germinate, invariably produce a [female] gametophyte; the 2 receiving a Y-chromosome produce a [male] gametophyte.[long dash]Female polycladous plants are sterile. Sporophytic offspring of polycladous [male] [male] X nonpolycladous [male] [male] produce tetrads each composed of 2 (genetically) polycladous and 2 nonpoly-cladous spores. The parental combinations of characters (2 [female] nonpolycladous, 2 [male] polycladous) are represented in these tetrads about twice as often as the "crossover" combinations (2 9 polycladous, 2 [male] nonpolycladous). The partial linkage between sex and vegetative character is hypothetically explained by a tendency for certain chromosomes derived from a given parent to remain together throughout the meiotic divisions. About 1/6 of the tetrads derived from matings of this type consist each of 1 [female] nonpolycladous, 1 [female polycladous, 1 [male] nonpolycladous, 1 [male] polycladous. The occurrence of a minority of such 4-type tetrads suggests that some segregation of chromosomes or of chromosome parts occurs in both meiotic divisions. Matings involving tuftedness as well as polyclady would be expected to yield, apart from certain apparently possible but rare combinations, 4 classes of 2-type and 8 classes of 4-type tetrads. All 4 of the former and at least 4 of the latter group of tetrad classes have been obtained from a limited number of matings.[long dash]The sporophytic character of spore-adherence or separation is governed entirely by the genetic constitution of the mother. In sporophytes derived from matings of S. texanus by S. donnellii, the characters of spore- and tetrad-walls resemble those of the maternal species. Something suggesting a predominant maternal influence in F1 gametophytes as well is shown by the total absence of semisterile plants among the progeny of typical [female] X semisterile [male] or of tufted [female] X semisterile [male]; also by the absence of cupulate plants in the progeny of typical [female] X cupulate [male].[long dash]Tufted races are apparently not uncommon in nature. Tuftedness is inconstant; a tufted clone bears a variable proportion of typical branches. Tufted clones are shown by matings to differ genetically from typical clones. The occurrence of clones showing markedly different proportions of typical branches suggests that tufted clones may differ genetically among themselves. This suggestion is confirmed by the results of matings of nontufted X much-tufted, little-tufted X little-tufted, little-tufted X much-tufted, and much-tufted X much-tufted. A factorial explanation of these results involves assumption of multiple cumulative factors, complementary factors, and certain linkage relations. Such an explanation may be simplified by assuming that, as in matings involving semisterility and cupulateness, certain factors contributed by a male parent may disappear or be inactivated in the progeny.[long dash]Continued selection within a tufted clone seems to result in the temporary establishment of sub-clones respectively more and less tufted than the original clone. Cessation of selection, however, results in a reversion of the sub-clones toward the original condition. The temporary effects of selection indicate that, within a tufted clone, tufted branches tend more strongly to give rise vegetatively to tufted, and typical branches to typical.

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