396 Mr Potter, On the junction of Root and Stem [May 28, 



I. Phoenix Dactylifera. 



In Phoenix Dactylifera there are generally in the root nine Xylem 

 bundles alternating with these nine Phloem bundles; (see figure n. 

 where the Xylem bundles are shaded ;) the central part of an older 

 root is composed of thick walled cells. Surrounding this as a 

 central axis we find the pericambium, and external to this the 

 endodermis. In older roots the endodermis is composed of thick- 

 walled cells and it is first seen where the fibrovascular bundles of 

 the root branch into the Cotyledons (figure in. where E is the 

 endodermis). The fundamental tissue lying outside the endo- 

 dermis contains numerous strands of sclereuchyma (B fig. II.) 

 arranged more or less in rings and large intercellular spaces. 



As we pass upwards from the typical structure of the root 

 towards the apex of the stem we find the Phloem bundles in- 

 creasing in size, assuming irregular V shaped forms, uniting and 

 anastomosing with each other; at the same time the Xylem bundle 

 has increased in size more especially at its external part where 

 the protoxylem is situated. As we approach the base of the 

 Cotyledon the Phloem bundles branch, sending branches into the 

 Cotyledon. The Xylem bundles now divide ; each branch from a 

 Xylem bundle unites with one from a Phloem bundle, and these 

 constituting a collateral bundle pass outwards into the Cotyledon 

 and unite with a strand of sclerenchyma which passes from the 

 root up into the Cotyledon. Thus in the Cotyledon there are as 

 many fibrovascular bundles arranged at nearly equal distances as 

 there were bundles of Xylem or Phloem in the root, the Xylem 

 being the most internal, the Phloem next, and the sclerenchyma 

 the most external constituent. 



Above the point of insertion of the Cotyledon with the stem 

 we find collateral bundles irregularly scattered, uniting with each 

 other in pairs and sending off branches into the leaves which 

 enclose the very short growing point of the stem (Fig. v. and VI.). 



II. Zea Mais. 



The stem of the Grasses is characterized by the presence of 

 nodes on the stem where the leaves are given off. Here the 

 fibrovascular bundles anastomose freely with each other, often 

 changing from one side of the stem to the other, the anastomosis 

 being so complete that it is often impossible to trace the separate 

 constituents of each bundle or the bundles themselves through the 

 node. 



The germination of Zea Mais is represented in Fig. vii. From 

 the seed S the edges of the scutellum Sc are seen ruptured by the 

 protrusion of the root R and the plumule. C is the so-called 

 Cotyledon, A the node from which it springs. At B is another 

 node, from which the fibrovascular bundles are given otf to the 



