TRANSACTIONS OF SECTION K. 1051 



6. Note, on the Anatomy of the Stem of Species q/ Lycopodium. 

 By C. E. Jones, University College, Liverpool. 



Ten species of Lycopodium haTe been examined ; among these two types may 

 be distinguished. 



1. Type of L. clavatum (L.). The oval stelic arrangement is marked by a con- 

 siderable amount of xylem, broken up into patches by bands of phloem. Centrally 

 these bands are strap-shaped, but at the ends of the long axes the areas of phloem 

 are external, and occur as curved and flattened wedges. Large cells without con- 

 tents, sieve-tubes, appear in the centre of the strap-shaped bands. Protophloems 

 and protoxylems are external, forming a continuous ring, as figured by Hofmeister; 

 so that, using De Bary's terminology, the arrangement of the bundles is radial. 

 Pericyclar and the so-called endodermal cells occur in concentric zones, 1-3 cella 

 broad. The former swell up, especially in glycerine or glycerine jelly ; the latter are 

 generally considerably lignified. The cells of the cortex lying just external to the 

 endodermal cells are thickened and lignified, forming a third concentric zone 

 several cells deep. To this type conform L. alpiiium (L.), L. phlegmaria (L.), 

 L. dendr aides (?), and L. cermcum (L.). 



2. Type of L. squnrrosum. The type which contrasts most markedly with the 

 former is found in L. squarrosum (Forst), L. dichotomton (Jacq), and L. num- 

 vmlarifoliuvi (Blume). The phloems occur as islands in the sea of xylem, or a.'* 

 inserted peninsulas. The phloems are centrally built up, with the apparent sieve- 

 tubes in the centre. Protoxylems are well marked, and lie externally, but proto- 

 phloems are not to be distinguished. Endodermal cells and pericycle are found as 

 in the previous type. The sclerenchymatous sheath is wanting, or very slightly 

 developed. 



The two remaining species, L. DalJwusieanum (Spring), and L. selago (L.) are, 

 to some degree, intermediate types. The phloem in L. DalhoJisieanum shows both 

 types, strap-shaped and centric. In the branches the structure becomes simpler. 

 There are two narrow strips of xylem, with an intermediate strip of phloem, so 

 that a prominent row of sieve-tubes occupies the very centre of the stelic cylinder. 

 L. selago in its structure is modified on that of L. clavatum. An interesting 

 feature of L, selago and L. squarrosum is the occurrence of root-structures running 

 through the stem. These consist of steles containing a crescent-shaped mass of 

 lylem, with protoxylems towards each tip, while the concave portion is filled up 

 with phloem. A characteristic sclerenchymatous sheath surrounds the stele. In 

 L. selago these root-structures are found even above the point where the stena 

 branches, but in L. squarrosum they have fused with the central cylinder before 

 branching occurs. 



MONDAY, SEPTEMBER 12. 



1. A discussion on the Alternation of Generations in Plants was 

 introduced by the reading of the following Papers by Mr. Lang, Professor 

 Klebs, and Mr. Wager. 



(o) Alternation of Generations in the Archegoniatce. By William H. 

 Lang, M.B., B.Sc, Lecturer in Botany at Queen Margaret College, 

 Glasgow University. 



[Ordered by the General Committee to be printed in extevso.'] 



One of the most important facts in the morphology of all plants higher 

 than Thallophytes is the occurrence in their life history of two alternating stages, 

 which difier widely from each other both in structure and reproduction. Of recent 

 years advances in our knowledge in several distinct departments of botanical 



