The structure & development of the mosses and ferns (Archegoniatae) . to sec-ondary chambers, which arenot, however, arranged inany regular order, and com-municate more or less with Fig. 13.—Piiiibriaria Californica (Hampe). A, Ver- c^wp pnnthprtical section through the apex of a sterile shoot, show-ing the formation of the air-chambers ; jtr, the apical In Ta7gionia (Figs, 16,cell, X300: B, similar section throueh an older part \ i ,i i of the thallus, cutting through a pore, X100. I 7)> whcre the archcgonia are borne upon the ordi-nary shoots, the growth of the dorsal segments is somuch g
The structure & development of the mosses and ferns (Archegoniatae) . to sec-ondary chambers, which arenot, however, arranged inany regular order, and com-municate more or less with Fig. 13.—Piiiibriaria Californica (Hampe). A, Ver- c^wp pnnthprtical section through the apex of a sterile shoot, show-ing the formation of the air-chambers ; jtr, the apical In Ta7gionia (Figs, 16,cell, X300: B, similar section throueh an older part \ i ,i i of the thallus, cutting through a pore, X100. I 7)> whcre the archcgonia are borne upon the ordi-nary shoots, the growth of the dorsal segments is somuch greater than that of the ventral ones that the upperpart of the thallus projects far beyond the growing point,which is pushed under toward the ventral side. A similarcondition is found in the archegonial receptacles of other forms,where this includes the growing point of the shoot (Fig. 19).In Targionia the lacuna; are formed much as in Fimbriaria,but they are shallower and much wider, and the pores corre-spondingly few. The assimilative tissue here resembles that. Ill MARCHANTIE^ 49 of Marchantia and others of the higher forms. It is sharply-separated from the compact colourless tissue lying below it,and the cells form short confervoid filaments more or lessbranched and anastomosing, and except in the central part ofthe chamber united with the epidermal cells. Under the pore,however, the ends are free and enlarged with less chlorophyllthan is found in the other cells. All of the Marchantiese except the aberrant genus Duinor-tiera correspond closely to one or the other of the abovetypes in the structure of the thallus, but in the latter the air-chambers are either rudimentary or completely absent, and theventral scales are also wanting. Leitgeb ^ investigated , whose thallus is characterised by a peculiar areolationcomposed of projecting cell plates, and came to the conclusionthat these were the remains of the walls of the air-chambers,whose upper parts, with the epid
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Keywords: ., bookcentury1800, bookdecade1890, bookidstructuredev, bookyear1895
