VIII 



MARATTIALES 



291 



ever, bath of Marattia and Angiopteris, there is but a single 

 axial bundle, as in the petiole of the cotyledon. 



Fig. 167, B shows a cross-section of a pinnule from a large 

 leaf of A. evecta, which has much the same structure as that of 

 Marattia. The central vascular bundle is horse-shoe shaped in 

 section, and shows a central mass of large tracheids with retic- 

 ulate or scalariform markings, surrounded by the phloem made 

 up of very large sieve-tubes much like those of Botrychium, 

 and with these are the ordinary protophloem cells and bast 

 parenchyma. A distinct bundle-sheath is absent, as, according 

 to Holle, it is from all the bundles in both Marattia and An- 

 giopteris, except those of the larger roots. The bulk of the 



Fig. i63.^A, Section of a large root of Angiopteris evecta, X14; m, mucilage duct; 

 B, part of the central cylinder, X about 70; en, endodermis. 



ground tissue is composed of large parenchyma cells, but on 

 both sides just below the epidermis is a band of colourless cells 

 which resemble exactly the collenchyma of Phanerogams. In 

 the base of the petiole this becomes harder and forms a colour- 

 less sclerenchyma, which in Dancea is replaced by brown scleren- 

 chyma like that of the true Ferns. In the lamina of the leaf in 

 Angiopteris too, the arrangement of the tissues is strikingly like 

 that of the typical Angiosperms. A highly-developed palisade 

 parenchyma occupies the upper part of the leaf beneath the epi- 

 dermis, which bears stomata only on the lower side of the leaf. 

 The rest of the mesophyll is composed of the spongy green 

 parenchyma found in the other Ferns. The smaller veins both 

 here and in Marattia have collateral bundles. 



