N. C. SttU CWkfi 



24 A TEXT-BOOK OF BOTANY. 



Numerous oil globules are also found in the protoplasm, and cal- 

 cium oxalate cr}'stals may occur in the cell-sap. 



Vaucheria furnishes an example of a plant whose interior is 

 not segmented by cell-walls. In other words, the cavity within 

 the outer or enclosing membrane is continuous, and such a plant 

 is said to be coenocytic, — i.e., like a syphon. But it should be borne 

 in mind that the plant contains a great many nuclei, and. as we 

 have seen (page 2), a nucleus with its associated cytoplasm 



Fig. 12. Vaucheria sessilis. A, sporangium from which the multiciliate zoospore is 

 escaping; B, resting zoospore; C, D, germinating zoospores with growing point (s); E, 

 plant showing root-Hke organ of attachment (w), spore from which the plant is developing 

 (sp); F, showing in addition two oogonia (og) and an antheridium (h). — After Sachs. 



constitutes a unit of work. Hence such a plant as Vaucheria is in 

 a certain sense equivalent to a plant having as many uninucleate 

 cells as it has nuclei. It would probably be better to call such a 

 plant multinucleate rather than unicellular. 



Reproduction by means of asexual spores is brought about as 

 follows (Fig. 12, A) : A cross wall is formed near the end of one 

 of the branches, the end portion constituting a sporangium. The 

 contents, including numerous nuclei, group themselves into one 

 large zoospore, which escapes through an opening in the sporan- 



