. Botany for agricultural students. Plants. VOLVOX 305 colony may divide into IG zoosporc-likc cells which remain together, escape from the mother colony, and thus become a new colony. The gametes are formed in essentially the same way as the individuals of the new colonies, but they separate and thus swim about independently after leaving the mother colony. When the zygospore germinates, as shown in Figure 260, there results a new colony which has only to grow to adult d '^ e Fig. 2G0. — Pandorina 77wrum. a, Motile colony ordinarily consisting of sixteen motile cells (X 475); b, colony
. Botany for agricultural students. Plants. VOLVOX 305 colony may divide into IG zoosporc-likc cells which remain together, escape from the mother colony, and thus become a new colony. The gametes are formed in essentially the same way as the individuals of the new colonies, but they separate and thus swim about independently after leaving the mother colony. When the zygospore germinates, as shown in Figure 260, there results a new colony which has only to grow to adult d '^ e Fig. 2G0. — Pandorina 77wrum. a, Motile colony ordinarily consisting of sixteen motile cells (X 475); b, colony in which the cells have fornaed daughter colonies (X 475); c, two gametes fusing; d, zygospore; e, zygo- spore germinating and forming a new colony. Redrawn with modifications from Oersted. Among the gametes there is often considerable variation in size and motility, some being smaller and more active than others. The gametes pair and fuse regardless of their size, and, when gametes that are unlike happen to pair, there is a suggestion of heterog- amy, although there is no distinct differentiation of gametes as occurs in plants where heterogamy is well established. Volvox. — The highest expression of colony formation is reached in forms like Volvox (Fig. 261), where the colony contains thou- sands of individuals held together in a gelatinous matrix and so arranged as to form a hollow sphere. The colonies of Volvox are often as large as a pin head and hence visible to the naked eye. The two cilia of each individual project from the colony, and by the lashing of the cilia the colony moves through the water bj' a revolving motion. One can often see them slowly moving about in ditches, ponds, and sometimes in tanks in greenhouses. A microscopical study of the colony shows that the individuals of the colony are connected by protoplasmic strands, and hence so. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readabili
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectplants, bookyear1919
