The Staining of living Nuclei, 575 



cleus lies almost entirely free, this does not interfere seriously. Longer 

 Immersion is apt to kill Ihe cells. 



Tiie stem-parenchyma of this species was also examined but with in- 

 different results. 



No other plants were as fully studied as the species of Tradescantia al- 

 ready described, but as will be seen from the following, a number of widely 

 separate forms were examined with similar results. 



Nitella flexilis. 



The spermatozoids of the Characeae being relatively large and easily 

 obtained, and also produced in great numbers, are about the best for stu- 

 dying these bodies. In order to obtain them it is necessary to place a ripe 

 antheridium upon the slide and carefully crush it in a drop of water. A 

 glance will show whether the spermatozoids are mature or not. In case 

 they are fully ripe, they will begin to escape from the mother-cells in about 

 an hour — somewhat later if they are not quite mature. The first experiments 

 with Nitella were made with methyl-violet. 



As soon as a sufficient number of the spermatozoids had escaped, a small 

 drop of a -l ^ Solution diluted with about twice as much water was run 

 under the cover-glass and allowed to remain about a minute. At the end 

 of this time both the swarming spermatozoids and those still in the mother- 

 cells were colored a pure blue. Those that were free continued to move for 

 some time, but came to rest much sooner than when unstained, the body 

 becoming at the same time deeper colored. 



Much better results are had when the Solution is weaker, and the action 

 more gradual. In this way an equally good color can be obtained with very 

 little diminution in the rapidity of the movement which however ceases as 

 a rule sooner than in the unstained spermatozoid. 



Dahlia operated much in the same way but the movement continued 

 somewhat longer. Here also a small amount of the staining fluid was used 

 and allowed to act somewhat gradually. 



Chara spec. (?) 

 An undetermined species of Chara growing in a pond in the Ttibingen 

 botanical garden was studied and the spermatozoids treated with mauvein 

 and dahlia with efl'ects similar to those described for Nitella. In this case 

 the coloring agents were applied both before and after the swarming had 

 begun, the antheridium being placed directly in a dilute Solution of the 

 staining fluid. The contained spermatozoids were quickly stained, but esca- 

 ped and swarmed in a perfectly normal way. The color was the same as 

 when they were allowed to escape before coloring. 



Ferns. 

 Owing to lack of good material only a few experiments were made 

 with ferns and these were confined to the sexual organs. It was found 



