Text-book of botany, morphological and physiological . plasm sepa-rates into tavo portions (see Han-stein). ist Case. Cell - DiiHsion ^vithContraction and Rounding-off of theDaughter-cells. a. A Cell-^vall is not secreted tilldaughter-cells, already isolated, hauebecot?ie completely separate. An ex-ample is afforded by the formation ofthe oospores of Achlya (Fig. 8). Atthe end of a sac-shaped cell or ofa branchlet of one, the protoplasmcollects, the larger end itself swellsup into a globular form [A, E),and, by the formation of a sep-tum (C), becomes an independentcell (the oogonium). Nucleus-
Text-book of botany, morphological and physiological . plasm sepa-rates into tavo portions (see Han-stein). ist Case. Cell - DiiHsion ^vithContraction and Rounding-off of theDaughter-cells. a. A Cell-^vall is not secreted tilldaughter-cells, already isolated, hauebecot?ie completely separate. An ex-ample is afforded by the formation ofthe oospores of Achlya (Fig. 8). Atthe end of a sac-shaped cell or ofa branchlet of one, the protoplasmcollects, the larger end itself swellsup into a globular form [A, E),and, by the formation of a sep-tum (C), becomes an independentcell (the oogonium). Nucleus-likestructures sometimes, but not usu-ally, form in the protoplasm (as in C). The whole protoplasmic body then breaks upinto two, three, four, or more parts, which very quickly round themselves off into aperfectly spherical form; (in a large number of observations I have never seen anintermediate form between C and Z).) The parts thus formed {e, e in Z)) contractviolently during their separation; i. e., their protoplasm becomes denser by expulsion of. Fig. 8.—Oogonia and antheridia of Achlya lignicola, growing on woodin water ; the course of development is indicated by the letters A—F. athe antheridium, b its sac penetrating into the oogonium (X550). ^ An exception occurs in the formation of spores of Anthoceros, where the nucleus of the mother-cell is not absorbed until four new nuclei are formed. ^ In Spirogyra, Mougeotia, and Craterospermum, the new nuclei only arise during the progressof the division of the protoplasm (De Bary, Die Familie der Conjugaten, Leipzig 1858). In theformation of the stomata of Hyacitithiis orie?italis, I was unable either before, during, or immediatelyafter the division of the mother-cell, to perceive a nucleus; it did not appear in any of the deriva-tive cells until a considerable time after the division. FORMATION OF CELLS. ^3 water; and only after they have become fertihsed by the antheridium-tubes («, l? inD) do they surround themselves w
Size: 1277px × 1955px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1870, booksubjectbotany, bookyear1875
