. Beginners botany. Botany. 200 BEGLVNEJiS' BOTANY dry weather the margins of the leaves roll inward, and the leaves fold closely against the stem, thus protecting the delicate assimi- lating tissue. The anthcriiUa and archcf^onia of polytrichum arc borne in groups at the ends of tlie branches on different plants (many mosses bear both organs on the same branch). They are sur- rounded by involucres of characteristic leaves termed pcricha'tia o\ pcncJuj:tal kaves. Multicellular hairs Vwoww paraphyses zxQ scattered among the archegonia and antheridia. The involucres with tlie organs borne wi
. Beginners botany. Botany. 200 BEGLVNEJiS' BOTANY dry weather the margins of the leaves roll inward, and the leaves fold closely against the stem, thus protecting the delicate assimi- lating tissue. The anthcriiUa and archcf^onia of polytrichum arc borne in groups at the ends of tlie branches on different plants (many mosses bear both organs on the same branch). They are sur- rounded by involucres of characteristic leaves termed pcricha'tia o\ pcncJuj:tal kaves. Multicellular hairs Vwoww paraphyses zxQ scattered among the archegonia and antheridia. The involucres with tlie organs borne within them are called receptacles, or, less appropriately, " moss ; As in marchantia, the organs are very minute and must be highly magnified to be studied. The antheridia are borne in broad cup-like receptacles on the antheridial plants (Fig. 297). They are much like the antheridia of marchantia, but they stand free among the paraphyses and are not sunk in cavities. At maturity they burst and allow the sperm cells or spennatozoids to escape. In poly- trichum, when the receptacles have fulfilled their fimction, the stem con- FiG. through a tjnues to grow from the oentre of RECEPTACLE OF PoLYTRi- the cup (///, Fig. 295). Thc arche- cHUM COMMUNE showing gonia arc bomc iu Other rcceptaclcs paraphyses and antheridia. " . 1 . r,,, ,-, ^ ^ ^ on different plants. 1 hey are like the archegonia of marchantia except that they stand erect on the end of the branch. The spojvgonjum which develops from the fertilized egg is shown in a, b, Fig. 295. It consists of a long, brown stalk bearing the spore-case at its summit. The base of the stalk is imbedded in the end of the moss stem by which it is nourished. The capsule is entirely inclosed by a hairy cap, the calyptra, b. The calyptra is really the remnant of the archegonium, which, for a time, increases in size to accommodate and protect the young growing capsule. It is finally torn loose and carried
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectbotany, bookyear1921
