186 



EDWARD C. JEFFREY ON 



cales is phyllosiphonic, and that of the Lycopodiales, on the other hand, is cladosiphonic. 

 The writer has reached the conclusion, for reasons indicated above, that the Equisetales 

 are likewise cladosiphonic. Assuming that the occurrence of cladosiphony in the two 

 groups is prima facie evidence of their relationship, it is necessary to add to this a number 

 of other features of similarity before it can be considered as proved that the Lycopodiales 

 and Equisetales are really somewhat closely allied. 



Goebel (Bot. zeit., 1887) and Buchtien (op. cit., p. 42) have both noticed the striking- 

 resemblance between the green gametophyte of Lycopodium inundatum and L. cemuum 

 and that of the genus Equisetum ; there are, in both eases, the same upright fleshy axis 

 and the same characteristically numerous lateral lobes. Goebel (op. cit.) has noticed, too, 

 that the archegonia of L. inundatum have the same relation to the lobes of the prothallus 

 as those of Eqnisetum. The archegonia of Equisetnm and Lycopodium are, moreover, 

 alike, in that in both genera they are uniformly without the basal cell, which is found 

 without exception in the archegonia of all the isosporous Filicales. 



The antherozoids of the two groups differ in structure, those of the Lycopods being 

 biciliate and moss-like, those of the Equisetaceae, on the other hand, being spiral and mul- 

 ticiliate. The embryo of Equisetum hiemale, as has been indicated in the earlier part of 

 this essay, resembles that of Lycopodium in that root and shoot both originate from the 

 upper (epibasal) region. But the resemblances are strongest in the sporophytic phases. 

 Both groups are palingenetically microphyllous and have invariably strobiloid fructifica- 

 tions. In both these features they present a very marked contrast to the Filicales. 

 Finally, both cohorts present the phenomenon of cladosiphony, and in this feature also are 

 contrasted to the phyllosiphonic Filicales. 



It may accordingly be assumed, if numerous features of resemblance are trustworthy 

 indications of relationship, that the Equisetales in the larger sense indicated above 

 and the Lycopodiales are closely allied, as indeed has already been suggested by Scott 

 (Pres. address Brit, assoc., 1896, p. 15) in connection with the genus Sphenophyllum. 



Conclusions. 



The conclusions of this research may be stated as follows: — 



1. The writer's investigation of the development of the vascular axis of the stem 

 of the young plant, in a large number of representative vascular cryptogams and 

 phanerogams, has led to the recognition of two primitive types of vascular axes viz., 

 the protostelic type consisting primarily of a single concentric bundle in the sense 

 of De Bary, and the siphonostelic type, in which the vascular tissues from the very 

 outset form a bundle-tube. Of siphonostelic axes there are again two types viz., phyl- 



