No. 450.] STUDIES ON THE PLANT CELL. 433 



drawing upon food that has been prepared for them and is either 

 stored in special structures (as seeds, spores, bulbs, etc.), or .manu- 

 factured in differentiated organs or tissues (leaves, chlorophyll 

 bearing tissue, phloem, etc.). The vegetative activities of body 

 plasm are far more specific than those of germ plasm. Their 

 tissues have particular and highly developed activities, some deal- 

 ing chiefly with photosynthetic processes, some (phloem) distrib- 

 uting the organized food over the plant body, some storing the 

 food in large quantities. Besides these there are mechanical 

 functions performed by highly differentiated tissues, even though 

 largely composed of empty cells, as the vascular tissue, support- 

 ing tissues, and the external protective integuments. 



It is not our purpose to discuss any of these vegetative activ- 

 . ities in detail, but only to distinguish as sharply as possible the 

 characteristics of germ plasm with its generalized activities from 

 the specialized body plasm. These generalized characters, as 

 before stated, are constructive activities which mean growth and 

 lead to nuclear and cell division. It is probable that any tissue 

 which presents them has regenerative powers that under the 

 proper environment might be expected to reproduce parts or the 

 entire organism. Germ plasm is distributed more widely through- 

 out the organism than is generally supposed, and many highly 

 specialized tissues still retain the spark of regenerative possi- 

 bilities. The significance of these conditions is not generally 

 appreciated, perhaps because the environmental conditions of 

 regeneration are little understood and are exceedingly hard to 

 adjust experimentally. There is presented here a very attractive 

 field of botanical investigation, a union of cell studies with the 

 more gross anatomical methods of experimental morphology. 



2. Cell Division. 



Cell division takes place only after periods of growth that 

 have led to a multiplication of nuclei and in the tissues of plants 

 above the thallophytes is very generally a part of the history of 

 each mitosis. This is because of the structure called the cell 

 plate which is essentially an organ of cell division. But the 

 thallophytes present other methods of cell division which bear 

 no especial relation to nuclear activities, and in certain groups of 



