404 BOTANICAL GAZETTE [November 



and Clapp (7). Garjeanne has done an extensive piece of work 

 in having examined over 30 species, and he concludes that the fungi 

 neither do harm nor good to the host plant. 



In transverse section, the rhizome of S. aspera is somewhat 

 irregularly oblong (fig. 7). The cells are undifferentiated except in 

 the central region, where there is a group of small, thick-walled cells 

 which stand out in sharp contrast with the much larger, thinner- 

 walled cells surrounding them. In longitudinal section they appear 

 as very narrow, greatly elongated cells, whose pointed ends dove- 

 tail into each other (fig. 8). Leitgeb (26, p. 69) gives the length 

 of the cells in 5. sinuata as 0.3 mm. and the breadth 0.009 mm. 

 In 6*. aspera the cells are o . 537 mm. long and o . 008 mm. in diameter. 



The aerial part of the thallus has the same general structure as 

 the rhizome (fig. 9). There is a central region of small, thick- walled 

 cells surrounded by broader, thin-walled cells, which together 

 form the midrib of the thallus. From the midrib the thallus 

 narrows abruptly into winglike extensions consisting of one layer 

 of cells. By treating the thallus, either the rhizome or aerial 

 parts, with Schulze's macerating solution, the cells of the central 

 area can be separated entire, and by staining them with Dela- 

 field's hematoxylin, the structure of the cell walls may be seen 

 distinctly (fig. 10). This treatment enables one to get a more accu- 

 rate measurement of their length, and it is also interesting to knew 

 that they remain intact after the action of this reagent. The cells 

 of the wing are disintegrated, but some cells surrounding the 

 central strand may remain intact provided the action of the 

 reagent is not too long (fig. 8). These long, narrow cells, with 

 their thick walls and spirally arranged pores, make Pallavicinia, 

 Hymenophyton, and Symphyogyna peculiarly interesting. They 

 were discovered by Sir William Hooker in 18 16 in Pallavicinia 

 Lyellii. In 1864 Gottsche (17) described them in S. sinuata. 

 Leitgeb (26, p. 69) describes the cells with their spirally arranged 

 pores, but he has no illustrations. Farmer (10) adds little to 

 Leitgeb's account, though he gives a good drawing of the trans- 

 verse section of the rhizome, and also one showing the lack of con- 

 tinuity between the strand of the main part of the thallus and that 

 of the ventral branch. Tansley and Chick (34) discuss fully the 



