. The structure and development of mosses and ferns (Archegoniatae). ly. In the Polypodiacese the sporangia, as is well knowm, ariseusually in groups (sori) upon the backs of leaves that differbut little from the ordinary ones. Sometimes, however, e. g.,Onoclea, they are very different, the sporangia being producedin great numbers, and the lamina of the leaf is much of the simplest cases is seen in Polypodiiim. Here thesporangia develop late upon ordinary leaves, and form scat-tered round sori, bearing, however, a definite relation to theveins—in this case forming above the free
. The structure and development of mosses and ferns (Archegoniatae). ly. In the Polypodiacese the sporangia, as is well knowm, ariseusually in groups (sori) upon the backs of leaves that differbut little from the ordinary ones. Sometimes, however, e. g.,Onoclea, they are very different, the sporangia being producedin great numbers, and the lamina of the leaf is much of the simplest cases is seen in Polypodiiim. Here thesporangia develop late upon ordinary leaves, and form scat-tered round sori, bearing, however, a definite relation to theveins—in this case forming above the free end of one of the 340 MOSSES AND FERNS CHAP. small veins. Where there are special sporophylls, the develop-ment of the sporangia begins before the leaves begin to Poly podium (Fig. 190) the first evidence of the forma-tion of sporangia is a series of minute depressions upon thelower side of the leaf, much as occurs in Angiopteris. Thebottom of this depression is occupied by a low elevation, theplacenta, and upon this the sporangia form in an analogous. St. B.
Size: 1907px × 1310px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorcampbelldouglashought, bookcentury1900, bookdecade1910
