]^yg THE MARATTIALES 



immediately surround the stoma. A section of the lamina presents an appearance 

 very much like that of Helminthostachys. Below the upper epidermis is a \yell- 

 developed palisade layer, while below this the spongy mesophyll has the characteristic 

 intercellular spaces found in the leaves of most of the higher plants. Danaa tricho- 

 manoides a very small species from Peru, has dehcate membranaceous leaves, which 

 probably'would show a much simpler structure than that of the coriaceous leaves 

 of the larger species. D. sintensis, a species from Porto Rico, which is in the herba- 

 rium of the British Museum, has adventitious buds developed at the leaf tip. 



cot 



C ' --" B 



Fig. 163. 

 A, B. Two longitudinal sections of a young sporophyte of Kaulfussia. 1^, /^, second 

 and third leaves; r^, second root. X20. 

 C. Stem apei. X180. D. Apex of third leaf. X180. 



THE APICAL GROWTH OF THE ROOTS . 



The earlier roots grow from a single initial cell, but this is later replaced by a 

 group of similar initials which, in the large roots, are very much like those described 

 for the root apex of Angiopteris (Koch 1). Figure 162 shows a section of a root 

 from the young sporophyte which is somewhat transitional in character between the 

 form with a single definite initial cell and the larger root with its group of initials. 

 The cell v, which is very much like the apical cell of the primary root, may perhaps 

 still be considered as the single apical cell, but the adjacent segments are almost 

 equal in size to this, and it is clear that they contribute to the plerome cylinder of 

 the root as well as to the cortex and the root cap. 



In sections of large roots taken from the adult sporophyte, there is found at the 

 growing point not a single initial cell, but a group of apparently similar initial cells 

 somewhat wedge-shaped in longitudinal section and arranged in a radiating fashion. 

 No single one of these can be clearly recognized as a primary initial cell. These 

 cells divide at intervals by longitudinal walls and from the bases additions are made 



