172 



EDWARD C. JEFFREY ON 



lar tissue which mark the nodes. It is impossible, however, even in the unbroken series of 

 thin sections, which the writer has studied, with the aid of phloroglucin and hydrochloric 

 acid, to be sure that such a union actually takes place, as the indications consist only of 

 somewhat irregular endodermal streaks radiating out from the internal endodermis, at the 

 points described above. From the state of affairs in the adult stem (Pfitzer, Pringsheim's 

 Jahrbucher, bd. 6; Van Tieghem, Journal de botanique, 1890, p. 365 et seq) , it might be 

 expected that we should find similar indications just above the nodes, but they do not 

 occur. 



The first node of the second shoot has likewise a pith of pericyclic origin. Here 

 again the internal endodermis makes its appearance only above the primary node. 

 The internal endodermis of the second shoot, however, is continuous throughout the 

 secondary axis and does not disappear at the nodes. It clearly unites moreover with 

 the outer endodermis below the nodal vascular rings. In subsequent shoots the internal 

 endodermis is likewise continuous and finally in shoots of five or more bundles it is 

 found also in the primary node and is continuous with the internal endodermis of the 

 parent axis. It is in shoots of five bundles that the internal endodermis first unites 

 with the external, above as well as below the nodes, as in the adult plant. The primary 

 axis does not develop nodal buds other than the basal one, except in some of its higher 

 nodes, and these seldom under ordinary conditions give rise to branches. The second, 

 third, and subsequent shoots have one or more dormant nodal buds at all their nodes. 

 Quite frequently there is an increase in the number of vascular strands in passing from 

 a lower internode to a higher one. In one example, where four strands were present 

 in the first internode, five were found in the second and six in the third, after which 

 the number remained constant. This feature is interesting, as repeating on a small 

 scale a phenomenon which was of common occurrence among the Calamites. 



Equisetum limosum is very similar to E. hiemale in the particulars of its internal 

 development. The only differences which need to be noticed are those which have 

 reference to the distribution of the endodermis. In the first shoot of this species, 

 whether bifascicular or trifascicular, there are no indications whatever of an internal 

 endodermis, although as may be seen from photograph 2 (PI. 28, fig. 2) the outer 

 endodermal sheath is well developed. The second shoot of E. limosum in my specimens 

 was too immature to show the endodermal marking. 



The arrangement of the endodermis in the young stems of these two species of 

 Equisetum does not appear to offer very much support to Van Tieghem's (Journ. de 

 botanique, 1890, p. 370) hypothesis of astely, for in accordance with his concep- 

 tion of the origin of astely, the primitive type had above the first whorl of leaves, 

 bundles individually surrounded by endodermal zones, and these individual zones 



