THE CELL 



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parent plant. Slime molds live in decayed wood and in order to 

 reproduce come to the surface, where they form fruiting bodies 

 containing the spores, which later germinate. These latter 

 swim about awhile as myxamoebae and then possibly 

 fuse or individually grow into the myxamoebae or 

 Plasmodia, which are the bodies of the plants. 



In comparing the Plasmodium of a myxomycete 

 with the body of an amoeba, we distinguish between 

 them in that the one is multinucleate and the other 

 uninucleate, yet Vonmiller has described an amoeba 

 with 12 nuclei. Here, as in all our attempts to define 

 and classify, Nature mocks our categories. She 

 seems at times to have had a clear-cut and carefully 

 thought-out plan according to which life forms have 

 developed, but there are examples, especially of 

 primitive organisms, which do not appear to fit into 

 any scheme. 



Built somewhat on the same principle as myxomy- 

 cetes, in that they possess anoncellular, multinucleate 

 body, are the coenocytic plants. To this type belong 

 bread mold and the green alga Vaucheria. Both 

 consist of a long tube, or coenocyte, containing many 

 nuclei but no orosswalls. Similar in structure are 

 the alga Cladophora and the stonewort Nitella the 

 individual cells of which contain many nuclei and 

 may reach 6 in. in length (Fig. 33). Valonia and its 

 cousin Halicystis are also large, multinucleate, 

 noncellular bodies. Both are relatively huge (1 to 4 

 cm.) spheres consisting of a large central vacuole 

 with as much as 50 cc. of sap, enclosed by a thin 

 layer of protoplasm. 



Not only are cells so constituted chemically as to 

 carry on their specific tasks, whether that of making 

 food or that of digesting it, but they are often equally 

 well fitted in a purely mechanical way. Examples such as 

 heavy-walled cells, spirally thickened ones, mechanical bracings, 

 and other structural features no less remarkable and perfect 

 from the point of view of engineering are familiar to the 

 plant anatomist. A most interesting case of a pure physical 

 adaptation is that of the cells of the protonema (filament) of 



Fig. 33.— 

 A cell of Ni- 

 tella. 



