36o 



MOSSES AND FERNS 



CHAP. 



the Osmundacese, the stem usually bifurcates once, into branches 

 of equal size, which may rarely fork once more. 



A section of the rhi- 

 zome (Fig. 203, B), 

 shows a massive cortex 

 composed largely of dark 

 sclerenchyma, but the in- 

 ner cortex is parenchym- 

 atous. The central cyl- 

 inder is bounded by an 

 endodermis, within 

 which are from one to 

 four layers of cells con- 

 stituting the pericycle. 

 Faull ( ( I ) , p. 7) was un- 

 able to verify Strasburg- 

 er's statement, that both 

 the endodermis and peri- 

 cycle in Osmund a, as in 

 the other Ferns examined 

 by the latter ((11), p. 

 449), are of cortical or- 

 igin. ^ 



. Inside the pericycle is 

 a continuous cylinder of 

 phloem, whose outer cells 

 constitute the proto- 

 phloem. The phloem 

 proper consists mainly of 

 sieve-tubes of large size 

 and with conspicuous 

 sieve-plates upon their 

 lateral faces. The so- 

 called "quergestreckte- 

 zellen" of Zenetti (Fig. 

 204, qu) are considered 

 by Faull to be sieve-tubes. 

 The woody strands form a reticulate cylinder, and in cross- 

 sections of the stem appear as a circle of horse-shoe shaped 

 masses of wood lying inside the phloem, and separated from 

 each other by the medullary rays. The tracheary tissue con- 



FiG. 203. — upper part of a sporophyll of O. Clay- 

 toniana, X2; sp, sporangia; B, section of the 

 rhizome of O. regalis, showing the arrange- 

 ment of the vascular bundles, X4 (after 

 De Bary). 



