Beer, Development of tlie pollen graiii and anther of some Onagraceae. 299 



I might occupy many pages in qiioting similar measure- 

 ments but as those wliich 1 liave already mentionecl are quite 

 typical of tlie rest it would serve no useful purpose to do so. 

 The general result lias been to sliow that in 0,6°,oNaCl. 0,75% 

 NaCl, 6 °/o cane-sugar, egg- white and the plants own juice the 

 protoplast has a very similar appearance and its measurements 

 agree very well witli one another at the different stages. 



Moreover, after remaining in these Solutions for some time 

 little or no alteration, either in size or appearance, was obser- 

 vable. The average measurement in these Solutions calculated 

 from all my notes are as follows; 



Pollen grain pollen cavity pollen protoplast 

 40 ^t 26 // 26 // 



62 ,1 37 fi '21 // 



70 '// 39 // 32 II 



74 // 42 II 34 . 25 ^i 



80 \i 46 [i 34.5 ,1/. 



Streng Flemmings Solution and streng chrom-acetic Solution 

 do not alter the protoplast very much in apj^earance but usually 

 cause some shrinkage. 



MerkeVs fluid was not so satisfactory and it causes the 

 vacuoles to swell up and the protoplast to enlarge. 



Absolute alcohol causes very considerable contraction of the 

 protoplast. 



Distilled water enlarges the vacuoles and causes them to run 

 together by breaking down the separating arms and laniinae 

 of cytoplasm. Consequently the whole protoplast swells up 

 greatly. 



Objection may still be taken to conclusions drawn from a 

 study of the living pollen in the plants own juice, the salt Solu- 

 tions and in egg-white, on account of the possible influence 

 which the mechanical Operation of teasing out the pollen grains 

 may have exerted. 



That mechanical disturbances can affect the living contents 

 of these cells is shown by the fact that if the pollen grains, in 

 e. g. 0,6 % Na Cl Solution, are covered by a cover glass and the 

 pressure due to this is not relieved the protoplast gradually en- 

 larges and may finally All the cell-cavity. If, however, the pre- 

 caution be taken, of preventing the pressure of the cover glass, 

 by a fragment of anther or Alter paper or by not covering the 

 preparation at all no such change takes place in the protoplast. 



An error from this cause, however, is extremely improbable 

 as the pollen grains can be drawn out from the anther without 

 actually subjecting them to the touch of an Instrument and with 

 only very little pressure or friction. This can be done by means 

 of the iibrous mucilage which surrounds the pollen grains and 

 binds them together in long strings. 



Moreover microtome sections of pollen grains, fixed whilst 

 lying untouched within the anther, show a rough parallel in 



