Manchester Memoirs, Vol. hi. (191 2), No. 11. 13 



tions on the stem internodes and leaf sheaths in recent 

 Equiseta. Both casts show the periodical appearance of 

 a shortened member at every 5th (or 6th) interval. One 

 table of measurements is given below, the other is 

 similar. For convenience of reading and comparison 

 with other tables, I have inverted it. 



Number. Position on Stem. Lentrth in mms. Period. 



D 

 C 

 B 

 A 



D 

 C 

 B 

 A 



E 

 D 

 C 

 B 

 A 



E 

 D 

 C 

 B 

 A 



E 

 D 



21 



20 



19 

 18 



17 

 16 



15 

 14 



1.3 

 12 

 1 1 



ID 



9 



8 



7 

 6 



5 

 4 



3 



2 



V. 

 Incomplete. 



IV. 



Complete. 



III. 



Complete. 



II. 



Complete. 



I Incomplete. 



Mr. Horwood says, " There is a noticeable increase, 

 regular and gradual, in each period, commencing at the 

 smallest internode. At the end of each period branches 

 were borne, indications of which may be seen on the 

 specimen." . . . This would place the branches in D 



* First internode from the base. 



