SELAGINELLA SPOROPHYTE 151 



Remove a rhizophore, which has grown down so as to reach 

 the soil, and wash it : observe 



4. The delicate roots, which rise at the point where the 

 rhizophores touch the soil, and branch in a monopodia! 

 manner ; and though they often seem to bifurcate it appears 

 not to be a case of true dichotomy. 



Observe further that many of the branches of the stem may 

 have a symmetrical arrangement of the leaves close to the 

 apex : these are the branches or cones, which bear the 

 sporangia : note that on these cones 



i. The leaves are all similar to one another and of small 

 size. 



ii. That they are arranged in four symmetrical orthostichies. 



iii. That on turning the leaves back, one sporangium will be 

 disclosed in each case. On comparing a number of sporangia 

 which have been exposed in this way, it may be seen that there 

 are two sorts of them 



a. Macrosporangia, which are of a green or light-brown 

 colour, and appear to be of rounded tetrahedral form. 



b. Microsporangia, which are more nearly spherical, and of 

 a reddish-brown colour. 



Note in older cones that the sporangia are already open, 

 dehiscence having taken place in a plane parallel to that of the 

 leaf. 



II. Cut out as thick a piece of the stem as can be found, and 

 about one inch in length : note a central white dot on the trans- 

 versely cut surface : this is the single central vascular bundle. 

 Slice off the upper surface of the stem with a razor till the 

 whole course of the vascular bundle is laid bare, and observe 

 with a lens 



1. The course of the central vascular bundle, which is 

 directly longitudinal and median. 



2. The smaller lateral bundles, which pass from the central 

 bundle without branching into the leaves, and traverse the 

 midribs of the leaves. 



III. Cut transverse sections of a well-developed stem : mount 

 some in glycerine, others in chlor-zinc-iodine : others again may 

 be mounted in acid solution of aniline sulphate. Examine first 



