510 MacDougal : Some Correlations of Leaves 



internodes, the basal one of which measured 14 mm. Two 

 branchlets were produced at the next node below on the newly- 

 formed portion of the main branch, which showed two and three 

 internodes and were 10 and 15 mm. long respectively. The 

 third internode below produced two branchlets 6 and 12 mm. 

 long and composed of two internodes. 



The lateral branchlets of the main branch showed less total 

 growth and also less marked development of the lateral bnds cor- 

 respondent to the general habit of the normal. Activity of the 

 vegetative points on the defoliated and normal branches had 

 practically ceased on June 15, the mutilated branch showing no 

 prolongation of the period. The departures from the normal 

 structure of the stem were fairly similar to those described in 

 Pnimis. Chlorophyl was quite as profusely developed in the 

 normal as in the treated branch, however, and was found in the 

 medullary rays in great abundance. 



The above results are found to agree in the main with those 

 of Boirivant, who practiced defoliation and delamination and noted 

 the effect upon stems and upon petioles of Faba vulgaris, Sa- 

 rothainmis scoparins, Genista tiiictoria, Lathynis odoratus, CJicno- 

 podiinn album, Atriplex nitens, Linum usitatissimum, Galium 

 Cruciata, Asparagus officinalis, Robinia Pseudacacia, Araclds 

 hypogaca and Ailantus glandidosa^' It is to be noted, however, 

 that the epidermal tissues in my material showed enlargement in 

 the tangential axis, and one or two other minor differences appear. 

 Boirivant's studies included a consideration of the anatomy of the 

 petioles of leaves of which the laminae had been cut away, and in 

 these organs he found an exaggerated production of chlorophyl, 

 modifications of the cortical tissues consisting of added differentia- 

 tions of palisade tissue, and enlargement of the vessels and more 

 lignification of the tracheids and pith. I am not able to find that 

 he noted the effects of the treatment upon the stipels of Robinia, 

 or made observations upon the reaction of the hypopodium 

 especially. 



The observations of Braun also extend over the matter of the 

 effect of delamination on stems. His observations included 



* Boirivant, A. Recherches sur les organes de remplacement chez les plantes. 

 Ann. Sci. Nat. Bot. VIII. 6 : 309-400. 1897. 



