98
VEGETABLE CELLS.
begun to decay, the contents (the mucilaginous layer withthe chlorophyll- and starch-globules) separate from thewall and lie effused in the cavity of the cell. In thiscase the new cells do not usually originate as small,colourless, homogeneous globules of mucilage, but aslarger globules of the confluent cell-contents, composedof mucilage, chlorophyll, and amylum. On the veryoutside a layer of homogeneous mucilage is always de-posited, and forms a sharply-defined surface. A distinctmembrane is quickly produced on this surface. The cell-contents are so arranged within this that the chloropliyll-and amylum-globules lie at the periphery, while themiddle part of the cavity is filled with transparent fluid.
These cells, whether they be formed within healthy ordecaying cells, originate through abnormal cell-formation,and stand, apparently, in no necessary relation to propa-gation ; therefore ordinarily they perish without furtherdevelopment. In isolated cases, however, they behavelike germ-cells (spores), and are developed into newplants.
In Plate II, figs. 1 and 2 represent an old utricle ofBryopsis Balbisiana, wherein abnormal cell-formation isoccurring. In fig 1, a and b, the cell-contents are deadand beginning to dissolve. They consist of scattered chlo-rophyll-globules and mucilage-granules. The partsc and d, on the contrary, possess active living contents,surrounded by a mucilaginous layer. They are connectedtogether by a mucilaginous cord: this cord is the rem-nant of the mucilaginous layer which formerly coated thepart a. In an earlier stage it was thicker, and is nowgradually becoming thinner. Pig. 2 represents the sameportion of an utricle some time later; the connectingcord of mucilage has disappeared, which has resultedfrom its becoming gradually thinner, until it was tornacross, and united perfectly with the two living portionsof the cell-contents, c and d. The former, c, is now adefined, ellipsoid portion of contents, altogether free, andcoated over its whole surface with a thin layer of homo-