938 REPORT— 1900. 



2. There are 2n bundles in the hypocotyl. As they descend into the root each 

 bundle rotates on its axis in such a way that the phloem groups are able to unite 

 in pairs. The xylem groups also unite in pairs, the protoxylem elements becoming 

 external as they do so. Thus there are n phloem and n xylem groups in the 

 root-stele. 



3. There are n bundles in the hypocotyl as in type 1, but in this case each of 

 the phloem groups divides into two without rotation. The branches from adja- 

 cent bundles unite in pairs, so that we still have n phloem groups in the stele. 

 Meanwhile each of the xylem groups has rotated on its axis without branching. 

 Thus the n xylem groups are all external. 



It is clear that type 3 is the converse of type 1. 



Among the monocotyledonous seedlings which I have examined I find a 

 fourth type of transition, which is the converse of type 2. The best example is 

 Anemarrhena aspkodeloides, but there are very clear traces of the same structure 

 in the allied genera Asphodelus and Asphodeline. 



The type may he thus defined : — 



4. There are n bundles in the hypocotyl. As they descend into the primary 

 rc^ot the phloem of each divides into two groups without rotation or subsequent 

 fusion. Thus there are 2n phloem groups in the root-stele. The xylem of each 

 bundle branches in two or more directions, while the protoxylem elements become 

 external. If more than 2n xylem groups have been thus formed, adjacent groups 

 fuse in pairs, so that only 2n xylem groups enter the root-stele. 



In Anemarrhena asphodeloides there are two bundles in the cotyledon which 

 pass downwards through the hypocotyl into the primary root. Daring the trans- 

 ition each phloem group divides into two. Each xylem group branches in three 

 directions. It sends a group of protoxylem elements to divide its own two phloem 

 groups from each other. This we may call the median protoxylem group. Two 

 lateral protoxylem groups are also formed from the xylem of each bundle in the 

 space dividing the bundles from each other. The four lateral protoxylem groups 

 thus formed are reduced to two by the fusion of adjacent groups in pairs. In the 

 end there are four phloem groups and four protoxylem groups in the root-stele. 



4. The Origin of Modern Cycads. By W. C. Worsdell, F.L.S. 



The subject is treated from the aspect of the vegetative structure. 



An exhaustive study of the vegetative characters enables one to draw theo- 

 retical conclusions as to the origin of modern Cycads. 



This conclusion is that the latter have descended directly from some Cycado- 

 filicinean type possessing the structure exhibited especially by such forms as the 

 Medullosa3 and Lyginodendrese, the chief point being that the collaterally con- 

 structed one or more vascular cylinders of modern Cycads have been derived from 

 one or more concentrically constructed cylinders of some Cycado-filicinean form. 



Those characters in the modern plants which approximate most nearly to the 

 primitive ancestral type are found in those parts of the plant where they would 

 most naturally be expected, viz. : — 



Of ai'za^ organs : the 2)rimary node or transitional region between stem and 

 root, and the Jlotvering axis ; of foliar organs : the cotyledon, the spoi'ophyll, and 

 the integument of the sporangium. 



In the axial organs or stems of modern Cycads the vascular tissue consists of, 

 in five genera, a single cylinder ; in the four remaining genera, of inore than one or 

 several cylinders. These cylinders are collateral in structure. 



In the region of the primary node, however, the structure of the one or more 

 outer cylinders exhibits a variation in that it approximates to the concentric type, 

 either by the appearance of an inversely-orientated zone attached to the inner face 

 of each cylinder, or by the breaking up of the cylinder into a number of concentric 

 or partially concentric independent strands. 



The first of these two types of primary nodal structure is normally charac- 

 teristic of Medullosa porosa, the second of Medullosa Solmsii. 



