VIRGULARIA MIRABILIS. 61 



leaves in each inch length of the i-achis. In tlie foUowinf,' table these 

 numbers are shown, as well as the " pitch " of the leaves at different 

 parts of the lenjith. By " pitch " we mean the number of pairs of 

 leaves per inch length of rachis ; c.;/., if in a given inch there are nine 

 pairs of leaves, then the " pitch " at that part of the rachis is 9 ; or 

 again, if in a given quarter of an inch there are four pairs of leaves, 

 this is at the rate of sixteen pairs in an inch, which is expressed by 

 saying that the " pitch " at this part is 10. 



The total length of the rachis in the Glasgow specimen is 'J inches, 

 and the pitch at different parts is as follows, commencing at the 

 upper end : — 



First inch — first ^ inch.. U pairs of leaves ;<.(?., pitch 72 



second J ,, . . (J ,, ,, ,, ,, 18 



second ^ ,, . . 4 ,, ,, ,, ,, 16 



second ^ ,, . . 7 ,, ,, ,, ,, 14 



Second ,, . . . . . . 9 ,, ,, ., ,,9 



Third „ 8 „ „ „ „ 8 



Fourth ,, 7i „ „ „ ,, 7i 



Fifth „ 7| „ „ „ „ 7| 



Sixth „ 8 „ „ ,, „ 8 



Seventh ,, 11 ,, ,, ,, „ 11 



Eighth 18 „ „ „ „ 18 



Ninth ,, — first i inch . . 12 ,, ,, „ ,, 24 



third I „ .. 17 „ „ „ „ 68 



Lower than this the leaves could not be accurately counted without 

 putting the specimen under the microscope, which we had no oppor- 

 tunity of doing. In Fig. 1, which is drawn from the Glasgow 

 specimen, the numbers along the left-hand side of the figure indicate 

 the pitch at the points opposite which they are placed ; the number 

 48, for instance, near the top of the figure, indicating that the pitch at 

 this point IS 48 — i.e., that at this point the leaves are at the rate of 48 

 to the inch. 



In the Oban specimens the tops are wanting, but the lower ends of 

 the rachis are, in four out of the seven specimens, perfect ; and in 

 these we have measured the pitch at different points, in order to 

 compare with the Glasgow specimen. In one specimen which we 

 select as apparently a fairly typical one, the total length of rachis is, 

 as in the Glasgow example, nine inches ; but as the top has gone, the 

 specimen when entire must have been considerably longer. The 

 measurements of this specimen are as follows, commencing at the 

 upper (truncated) end : — 



