244 BOTANICAL GAZETTE [march 



Fig. 12 shows a number of the spindle-shaped ones at a higher 

 magnification. The pit pores have been outlined for greater 

 clearness. The second type of torus occurs in the immature wood 

 of the stem and occasionally in the root. Fig. 19 shows a trans- 

 verse section from the cambial region of a young rhizome of B. 



num. The tracheids are only slightly lignified, some still 

 showing the contents. Here the torus is a short oval structure as 



Fig. 19. — Botrychium obliquum: transverse section of young rhizome, at cam- 

 bium showing torus and double membrane; X600, 



long as, or slightly longer than, the pore of the pit, and connected 

 to its edges by a fine membrane. 



This section (fig. 19) also illustrates a feature which I have 

 observed in other forms, that is, the double nature of the membrane. 

 In the pit of the tracheid at the left-hand lower corner the mem- 

 brane is of a double character. The tracheid lies against a paren- 



chyma cell of the ray, and only the half of the membrane next to 

 the wood cell has been thickened, while that lying next to the ray 

 cell remains uniform. The same double nature and plano-convex 

 thickening of the membrane are shown in the third cell to the 



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right. Here a tracheid, as yet unlignified and filled with contents, 

 is adjacent to one which is more advanced in development, and 

 the thickening occurs only on the side of the latter. 



