144 



The Irish Naturalist. 



September, 



long naked tail.^ Cone small, seldom present, rather 

 slender, yellowish, on a pinkish peduncle about J inch long. 

 Stem about 8 mm. in circumference, somewhat firm, yielding 

 elastically to lateral pressure, furrowed, but less so than in 

 nrvense. Teeth about 12, crowded, very narrow, 2.5 — 3 mm. 

 long. Central hollow |-| the diameter, the lacunae in 

 the wall oval, small, larger and rounder than in limosiim, 

 as large as or smaller than in arvense, their longer axis 

 transverse as in limosum, not radial as in arvense. Layer 

 of thickened cells absent as in limosum. 



It will be seen that this more minute comparison amply 

 bore out the first impression of the intermediate character, 

 as between E. arvense and limosum, of the plant under 

 discussion. Several considerations, particularly the colour 

 of the plant and the characters of the cone, ruled out 

 E. palnstre as a possible parent. There the matter had to 

 rest until return home rendered books and specimens 

 available. It then became clear that the Hilltown plant 

 agreed well in all essential characters with E. litorale Kiihle- 



i The relation of the branched to the unbranched portions of the stems 

 in the Hilltown plant may be shown as followS; the figures given being 

 the average of a number of stems examined. The joints are counted 

 from the tip down to the uppermost joint which bears roots. 



Number of Joints 



Unbranched upper part 

 Branched middle part 

 Unbranched lower part 



Total 



The fertile stems, in spite of the smaller number of joints, attain the 

 same total length as the barren stems, owing to the much greater length 

 of the internodes in the unbranched upper section (see Plate VI., 1,2). 

 The numbers of which the averages are given above all vary from about 

 \ more to | less. 



