Chap, i The Cell 



177 



Hick observed continuity between cells of certain 

 Fucaceae in 1885. A contribution to the subject was 

 made in 1891 by Kienitz-Gerloff, who relied on swelling 

 the wall with sulphuric acid and . subsequent staining. 



In 1893 a new method was introduced by Poirault ; he 

 killed pieces of various tissues by soaking them in a 

 dilute solution of iodine. The subsequent treatment 

 differed little from that of his predecessors, but the 

 preliminary fixing of the protoplasm by the iodine was 

 advantageous. 



Gardiner took the subject up again a few years later 

 and published some very important results in 1897. To 

 kill and fix his tissue he employed a mixture of osmic acid 

 and uranium nitrate, and he stained it subsequently with 

 saffranin. The new reagent enabled the stain to penetrate 

 the tissue much more readily, and so to reach the more 

 delicate of the threads. 



He was able to show that in the case of pitted cells the 

 pit-closing membrane is always traversed by threads of 

 protoplasm, and that other threads traverse the general 

 wall. In non-pitted cells the wall is perforated by the 

 threads, though there are no pits. The threads are arranged 

 in bundles in a manner recalling the disposition of the 

 achromatin fibrils which accompany nuclear division. He 

 carried the work out more completely than in his earlier 

 paper, and showed that the structure exhibited by endo- 

 sperm tissue is in all respects entirely typical of plant 

 tissue generally. In epidermal cells he found that the 

 external walls are penetrated by threads as far as the 

 cuticle, but that the latter blocks their way to the exterior. 

 He claimed to trace the threads to the fibrils of the 

 nuclear spindle which become imprisoned in the newly- 

 formed cell wall. 



In a further paper, published in 1900, he showed that 

 in certain cases a dot can be distinguished on the thread 



? GREEN M 



