IN VEGETABLE BIOLOGT. G07 



many large beads threaded upon a string made up of conjoined 

 canals and rings. Similar but smaller rings are interposed be- 

 tween tbe central and intermediate cells. The protoplasm of the 

 pit comes flush up with the contour of the ring, and remains in 

 close connection with it, and this makes discovery of the mem- 

 brane-piercing threads difficult. 



The small outer cells present a type of continuity already 

 dwelt upon. Each cell, polyhedral in outline, and with a dense 

 layer of protoplasm placed, with but a few small intervals, against 

 the whole wall, is connected with its circumjacent fellows by a 

 single fine filament, at or near the centre of which is placed a 

 bright bead-like particle, similar to those on the connecting- 

 threads of Chondrus and Polyides (tig. 27). Examination with a 

 high power (900 diameters) failed to indicate any division of the 

 thread in passing the bead. By studying the development of 

 the beads it is shown that they are of the same nature as the 

 rings, but they differ from them in not being provided with a 

 membrane. 



Cebamium bubbum, var. — In longitudinal section are seen a 

 central row of long, nearly rectangular, surrounded by a number 

 of small cortical, cells; others, intermediate in size, occupying the 

 interval between the pairs of large cells, as well as forming a con- 

 tinuous layer immediately investing them. In the floor of the 

 central cells is a small ring, the membrane of which is perforated 

 at several points of its circumference, and occasionally elsewhere. 

 Threads of protoplasm pass through the perforations, and con- 

 nect the protoplasts. The cortical cells resemble those of the 

 form last mentioned. 



The thallus of Laubewcia hybbida is made up of external, 

 nearly isodiametral, and a central core of cells lengthened in the 

 direction of the axis of growth. The walls of either type are 

 greatly thickened. The protoplasts are connected with their 

 neighbours by strands which run up the pits, each to a single 

 riug, undivided through the centre of the membrane of which, or, 

 as is usually the case, divided at its circumference or whole face, 

 it passes into the contiguous pit. 



Chylocladia abticttiata.— The branches, resembling those 

 of an Opuntia in miniature, consist, in fully grown parts, of a 

 series of chambers, of which the roof and floor, situated at the 

 narrowed portions, are made up of several layers of short cells. 

 Cells many times longer than broad occupy the centre of a young 



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