Cucurhita maxima and C. Pejpo. 51 



Interior to the wood zone is the remaining portion of the 

 fundamental tissue. In the outer portion of this, the vascular 

 bundles already referred to arise, while the inner portion re- 

 mains as a pith region and often shrinks away from the center, 

 developing a lysigenetic air cavity, thus leaving the basal por- 

 tion, of the tendril arm like the petiole from which it arises, 

 hollow. 



That these various tissues bear an important relation to the 

 movement of the tendril and its power to grasp an object or 

 coil up without contact, is most certain, and what these rela- 

 tions are will be seen after we have considered the motions 

 themselves. 



We should also remark, in passing, that this structure is not 

 peculiar to the tendril arm, since in all its essential features, 

 i. e., collenchyma, vibrogen and woody tissue, the same struct- 

 ure is to be observed in the petioles of both tendrils and normal 

 leaves, with this difference, however, that in these latter, the 

 vibrogen is found in more than three bands, and these are 

 arranged at tolerably regular intervals about the circumference 

 of the petiole. 



(b.) The recent developments concerning the continuity of 

 protoplasm in vegetable tissues, at once served as a suggestion 

 that in active tendrils this continuity should be found, if any- 

 where, and that it must doubtless furnish an important clue 

 to the proper explanation of many phenomena connected with 

 movement of the tendril itself. 



Thin transverse sections of the tendril were treated upon a 

 glass slide while yet quite fresh, with concentrated sulphuric 

 acid for a period of two or three seconds, at the end of which 

 time they were quickly immersed in water and thoroughly 

 washed to remove all acid. Care must be taken not to allow 

 the action of the acid to proceed too far, or both structure and 

 protoplasm will be destroyed. If successful, the cell walls 

 should be strongly swollen, but not broken. 



After washing in water, the sections were stained in picric 

 aniline blue,* being allowed to lie in the stain for ten min- 

 utes. At the end of this time they were thoroughly washed to 

 remove all the picric acid, as is indicated by the failure to dis- 

 charge any more yellow, and a change of color in the sections 

 to a well-defined blue. The results are best when the alcohol 

 washing succeeds in removing all the picric aniline from the 

 cell walls, but leaves a maximum of aniline blue in the proto- 

 plasm. At the end of this treatment the sections were mounted 

 in 25 per cent glycerine for examination. 



* This is essentially the stain recommended by Gardiner (Phil. Trans., 1883, 

 p. 817), and was prepared by saturating a 50 per cent solution of alcohol wilh. 

 picric acid. To this add BB blue untD a dark greenish blue solution is produced. 



