. Text-book of botany, morphological and physiological. Botany. FILICINEM. 447 in Salvinia, they form the free neck-portion (which in Marsilia projects only slightly, in Pilularia very much) and the ' closing cells' of the archegonium. Above the central cell, the protoplasm of which contracts, a small canal-cell is visible, according to Hanstein, penetrating between the ' closing cells/ and behaving as in Salvinia. Hanstein was unable to recognise any further cell-formation within the central cell, and he concluded that the whole of its protoplasmic body was converted into the oosphere; Jancze
. Text-book of botany, morphological and physiological. Botany. FILICINEM. 447 in Salvinia, they form the free neck-portion (which in Marsilia projects only slightly, in Pilularia very much) and the ' closing cells' of the archegonium. Above the central cell, the protoplasm of which contracts, a small canal-cell is visible, according to Hanstein, penetrating between the ' closing cells/ and behaving as in Salvinia. Hanstein was unable to recognise any further cell-formation within the central cell, and he concluded that the whole of its protoplasmic body was converted into the oosphere; Janczewski, however, found here also the ventral canal-cell which occurs in other Vascular Cryp- togams, as a small mass of protoplasm cut off from the central cell. After fertilisation the layer of tissue of the prothallium surrounding the central cell becomes double; a few chloro- phyll granules arise in it, and the outer cells grow in Marsilia Salvatrix (Fig. 315) into long root-hairs, which are especially luxuriant when no fertilisation takes place. In the case of Marsilia Salvatrix the antherozoids collect in large numbers at the time of impregnation in the funnel above the prothallium, and force themselves into the neck of the archegonium. Development of the Asexual Generation, The first processes of division by which, in Salvinia, the oospore is transformed, after fer- tilisation, into the embryo, have been most ac- curately described by Pringsheim. The first division is effected by a wall (basal wall) which separates the posterior (hypobasal) half of the oospore, above which is the mouth of the archegonium, from the anterior (epibasal) half, which is usually larger; this wall is nearly per- pendicular to the median line of the prothallium. The two cells are next divided by walls (trans- verse) nearly at right angles to the previous one. If the angle enclosed by these two walls is bisected by a straight line (Fig. 313, A, c, d), this line represents the axis of growth of the s
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectbotany, bookyear1882
