244 botanical gazette. [ October, 



needs of the plant bring from this common source the micro- 

 scopic organs for assimilation, for storing up starch in the 

 form of grains, for protection and attraction. This most in- 

 teresting generalization in regard to the granules taken to- 

 gether, adds a new zest to the study of the developing plant 

 and the evolving species. 



It has been lately claimed by de Vries of Holland, that 

 the sap-cavities or vacuoles in protoplasm divide in much the 

 same way as do the granules just referred to, but this part of 

 the subject is not yet beyond all doubt. That the sap cavi- 

 ties are the birthplace of most crystals, and that the aleurone 

 •rains may be desiccated sap cavities has been made out by 

 several observers. But it is not clear that vacuoles divide as 

 granules do. What we do know beyond all reasonable question 

 is this — that all the working granules within the plant have 

 sprung from pre-existent granules, and that there is no break 

 here in the transmission from parent to offspring. 



Such, then, are some of the more important changes 

 which have taken place with regard to our knowledge of the 

 living contents of vegetable cells. I would gladly take the 

 time, if it could be granted, to call your attention" to certain 

 most interesting discoveries which have been made by Pfef- 

 fer relative to the absorption of coloring agents by living pro- 

 toplasm, and which have been supplemented bv "Campbell in 

 regard to the nucleus. But more than this allusion is now 

 impossible. 



It is an interesting coincidence that with the substitution 

 of the crude compound microscope for high power simple 

 lenses in 1660, came the first works on vegetable structure, 

 and for more than one hundred years, or until the introduc- 

 tion of achromatic object glasses, these works were in truth 

 the only authoritative treatises. With the introduction of 

 water-immersion lenses came renewed activity in this field, 

 and with the later discovery of homogeneous immersion 

 lenses came the results which have now been detailed. 

 Whether we have, at these stages, more than a series of in- 

 teresting and very striking coincidences, or not, we have not 

 time now to discuss. It is enough for our present purpose to 

 observe that, with the introduction of the cedar oil immersion 

 objectives, a thorough reinvestigation of certain parts of this 

 subject began. One maybe pardoned for asking whether 

 the objectives known as apochromatics are to open up in this 

 field new lines of research. 



Can these recent discoveries relative to the continuity ot 



