Vl] VARIOUS TYPES OF CELLS 77 



and other vascular Cryptogams, indeed, the escaped proto- 

 plasmic contents do not clothe themselves, but die if 

 they do not reach their destination, the protoplasm of 

 another naked cell. 



The student is now in a position to apprehend generally 

 the meanings which have been attached to the word 

 " cell " in its various vicissitudes in the history of Botany. 

 Originally applied by Hooke with its ordinary signifi- 

 cation to the cell-cavity with its boundary wall only, it 

 came to connote the cell-wall plus its protoplasmic and 

 other contents, and finally was extended to signify the 

 living protoplasm only. 



Now, since the protoplasm is the essential part of the 

 cell, and may produce all the other parts, we may term 

 such a naked cell as a zoospore, oosphere, antherozoid, 

 Myxanioeba, &c. a Primordial cell. Then in cases where 

 the primordial cell has clothed itself with a thin cell-wall 

 and is in train to become vacuolated and develope further, 

 we may speak of an Embryonic cell. When the cell-wall 

 and vacuoles exist in their typical form, and the proto- 

 plasm shows "itself differentiated into cytoplasm, nucleus, 

 chlorophyll-corpuscles and plastidia, and other typical cell- 

 contents, we have the Typical cell ; and, finally, in those 

 cases where the cell-wall alone is left, the term Cell- 

 chamber may be employed. This leaves us free to use 

 the word "cell" in its perfectly general sense, as is so com- 

 monly done, and the various kinds of cells can then be 

 dealt with, and special names given to them as occasion 

 demands. The term Cell-tissue then means merely a 

 group of cells, without prejudice as to the kinds of cells 

 meant : the various kinds of cell-tissues will receive their 

 special names according to peculiarities to be recognised 

 later. 



It merely remains to add, for the general purposes of 



