SHOWING STRUCTURE, FROM THE RHYNIE CHERT BED, ABERDEENSHIRE. 783 



Fig. 43. Longitudiual section of stele of the upper region of an aerial stem, i.e., inner cortex ; ph., 

 phloem ; x., xylem. x 60. (Slide No. 2415.) 



Fig. 44. Transverse section of small stele to show the phloem. ph., phloem; *., xylem. x 160- 

 (Slide No. 2391.) 



Fig. 45. Transverse section of xylem of stele represented in fig. 41. ph., phloem; x., xylem. > 160. 



(Slide No. 2391.) 



Fig. 46. Transverse section of the stele of the small stem shown in fig. 25. i.e., inner cortex; ph., 

 phloem ; x., xylem consisting of two tracheides. x 160. (Slide No. 2416.) 



Fi"s. 47 and 48. Longitudinal sections of the xylem showing the broad annular thickening of the walls 

 of the°tracheides. x 250. Fig. 47 (Slide No. 2403). Fig. 48 (Slide No. 2400). 



Fig. 49. Part of an oblique section of an aerial stem showing the epidermis (ep.) in surface view, and 

 also a surface view of one of the small projections (pr.). x 60. (Slide No. 2390.) 



Figs. 50 and 51. Two longitudinal sections passing through small projections, ep., epidermis; o.c, outer 

 cortex; i.e., inner cortex, x 60. Fig. 50 (Slide No. 2390). Fig. 51 (Slide No. 2415). 



c 



Platk VIII. 



Figs. 52, 53, and 54. Examples of small projections (pr.) bearing rhizoids (rh.) shown in transverse 

 sections of stems. Figs. 52-53, x 60. Fig. 54, x 160. (Slide No. 2389.) 



Fig. 55. Transverse section of a stem showing two projections (pr.) and a partially separated branch (t>r.) 

 which is leaving a scar (sc). x 60. (Slide No. 2413.) 



Fig. 56. Obliquely transverse section of a stem bearing a lateral branch (br.) attached by a fairly broad 

 base. The adventitious branch appears to be itself branching, x., xylem of parent stem ; x '., xylem of 

 branch, x 20. (Slide No. 2409.) 



Fig. 57. Transverse section of stem with an adventitious branch (br.) attached by a fairly narrow base. 

 x., xylem of parent stem ; x '., xylem of branch. x 20. (Slide No. 2402.) 



Fig. 58. Longitudinal section from the higher region of the stem showing on the right a branch (br.) 

 with a fairly wide base, while on the left the base of another branch is cut obliquely. x 20. (Slide 

 No. 2414.) 



Fig. 59. Longitudinal section, becoming oblique on the left, of a stem with well-marked tissues. The 

 branch (br.) is attached by a broad base, ep., epidermis; o.e., outer cortex; i.e., inner cortex; ph., phloem; 

 .<-., xylem of parent stem; x'., xylem of branch. x 20. (Slide No. 2401.) 



Fig. 60. Transverse section of a stem with a small projection (pr.) and a branch (br.) attached by a very 

 narrow base. The branch has no stele, and a transverse section of another small axis without a stele lies 

 beside it. x 60. (Slide No. 24.13.) 



Fig. 61. Median longitudinal section of a stem showing at br. and br 2 . the bases of two lateral 

 branches. No vascular connection exists between these and the parent axis, x., xylem of parent axis; 

 x., xylem of one of the branches. x 20. (Slide No. 2404.) 



Plate IX. 



Fig. 62. Slightly tangential longitudinal section of a sporangium terminating a fairly stout stem. The 

 sporangium, which is filled with an enormous number of spores, is lying in the peat. x 5£. (Slide 

 No. 2393.) 



Fig. 63. Small empty sporangium (sp.) borne on a slender stem (ax.) and lying in the peat. x 5|. 

 (Slide No. 2392.) 



Fig. 63a. The sporangium shown in fig. 63 more highly magnified, ep., thick-walled epidermis ; tap., 

 tapetal layer; x., xylem of axis; a, accidentally contracted junction of axis and base of sporangium. x 20. 

 (Slide No. 2392.) 



Fig. 64. Longitudinal section of another sporangium showing the pointed apex, x 7. (Slide No. 2396.) 



Fig. 65. Two sporangia (s. and s'.) cut transversely as they lay side by side in the peat. x 14. (Slide 

 No. 2411.) 



Fig. 66. Portion of the sporangium &. in fig. 65 more highly magnified, ep., thick-walled epidermis ; 

 m.l., decayed middle layers of wall; tap., tapetum ; sp., spores. x 60. (Slide No. 2411.) 



