. Dansk botanisk arkiv. Plants; Plants -- Denmark. F. Børgesen: Rhodophyceæ of the Danish VV. Indies. 349. each other while in the other species of Martensia this arrangement is not found at all or at any rate only slightly indicated. According to Svedelius the coherent tissue of the young frond is formed by filaments congenitally connate just as in the case of the other Delesseriaceæ. Later on intercalary cell-divisions contri- bute to the growth of the tissue. When the coherent tissue has reached a certain breadth the development of the net begins. Some large cells, becoming the basal ones o
. Dansk botanisk arkiv. Plants; Plants -- Denmark. F. Børgesen: Rhodophyceæ of the Danish VV. Indies. 349. each other while in the other species of Martensia this arrangement is not found at all or at any rate only slightly indicated. According to Svedelius the coherent tissue of the young frond is formed by filaments congenitally connate just as in the case of the other Delesseriaceæ. Later on intercalary cell-divisions contri- bute to the growth of the tissue. When the coherent tissue has reached a certain breadth the development of the net begins. Some large cells, becoming the basal ones of the net, are formed along the margin and from each of these a row of cells grow up; these cell rows are mutually free with the exception of the uppermost cells of the rows which at both sides all are connected to- gether with those of the neighbour cell-rows. From these connected cells the next belt of coherent tissue originates (comp. ).Thefiee rows of cells are running nearly parallel to each other; their cells are soon divided by horizontal walls (lying in the plane of the thallus), the cell-rows herewith being transformed into lamellæ. In this way the longitudinal beams of the net are formed. About the same time when divi- sion of the cells takes place in the longitudinal rows of cells the cross-beams of the net begin to grow out. In Martensia Pa- vonia these are formed in such a way that a cell in the longitudinal cell-row grows out unilaterally in the direction of the neighbour cell- row (comp, the fig. 33 of Svedelius). This outgrowth, being separated from the mother cell by a wall, soon reaches the opposite cell-row and then grows together with it in a way very similar to that found e. g. in Dictyurus, Microdictyon etc. In forming the cross-beams in this way Martensia Pavonia differs for instance from Martensia fra- gilis in which two outgrowths issue oppositely from each cell; these outgrowths meet those issued from the neighbour cell-rows half-way and gro
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