9. 



are tliur. le^'t two mar.^imil oellc of Die fiftli fn-ade in eacli 

 segment. T}ie next v;all forced in each of tiiose may }iave 

 eitlier one of tv.^o positions. In the more frequent tj-po of 

 division, ajiother lonr^itudinal anticline appears in each 

 ( V,Fip;. 13 ) paralell to wall III, formin.P- thus the fiftli 

 and last section and leavinrr an ultimate marginal cell of 

 the sixth grade. Then a pericline appears, runnin;r!: from 

 wall IV to wall V , and tlie function of the marginal cell 

 as sucli is tlius ended. In tlie otlier aiid less frenuent type 

 of division, th.e marp;inal cells of tlie fifth ,f^rade are di- 

 vided iiimediatelj'" "by periclines runnin.^;- from wall III to 

 wall IV J the marginal cell of the fifth grade playing the 

 sarae role Iiere as tliat of tlie sixth, grade in th.e first t^-pe; 

 and their furtiier development is also practically the same 

 in botli cases. The fate of all the segments of the leaf is 

 in otiier respects tlie SEi:ne, with, th.e exception of those 

 giving rise to the lamina and to the sporocarp, in vrhich. 

 tlie pericline is never formed in the marginal cell. 



'TJie Petiole, 



Talking the first type of leaf for the study of the 

 further development of the se.nj'ients of the petiole, we find 

 that diu'inr tlie divisions of tlie tertiary marginal cells, 

 sections I and 11^ and the other sections as fast as formed^ 



