IX 



MARA TTIA CE^—ISOE TA CE.-E 265 



unable to make out a single initial in Ajigiopteris, which other- 

 wise agrees closely with Marattia. 



The study of the root was confined mainly to the older 

 embryos, and although some variation is noticed, it is pretty 

 certain that there is a single apical cell, not unlike that found 

 in the Ophioglossaceae. Whether this can be traced back to 

 one of the primary hypobasal octants, it is impossible now to 

 say; but Farmer's^ statement that in Angiopteris there is at 

 first a three-sided apical cell would point to this. Unfortunately 

 my own preparations of 2Iarattia were too incomplete to 

 decide this point in the latter. In the older root the form of 

 the apical cell was usually a four-sided prism, from all of 

 whose faces segments were cut off, although sometimes an 

 approach to the triangular form found in the Ophioglossaceae 

 was observed. 



The foot is much less prominent than in BotrycJiiuvi, and 

 in this respect the Marattiaceae are more like OpJiioglossumr 

 In Mat-attia all the superficial cells of the central region of the 

 embryo become enlarged and act as absorbent cells for the 

 nourishment of the growing embryo. 



As the embryo grows, the surrounding prothallial tissue 

 divides rapidly, and a massive calyptra is formed which com- 

 pletely encloses the young sporophyte for a long time. Owing 

 to the position of the cotyledon and stem, which grow up 

 vertically through the prothallium, a conspicuous elevation is 

 formed upon its upper side, through which the cotyledon finally 

 breaks. A similar elevation is formed by the calyptra upon 

 the lower side, through which the root finally penetrates, but not 

 until after the cotyledon has nearly reached its full development. 

 The prothallium does not die immediately after the young 

 sporophyte becomes independent, but may remain alive for 

 several months afterwards, much as in BotrycJiiuni. 



The first tracheary tissue arises at the junction of the bundles 

 of the cotyledon, stem, and root. These primary tracheids are 

 short and their walls are marked with reticulate thickenings. 

 From this point the development of the tracheary tissue, as 

 well as the other elements of the bundles, proceeds toward the 

 apices of the young organs. The formation of the secondary 

 tracheids is always centripetal. 



Short hairs with cells rich in tannin, and staining strongly 

 1 Farmer (3), p. 268. 2 Mettenius (2), PI. XXX. 



