184 EDWARD C. JEFFREY ON 



was protostelic and L. harcoifrfii was siphonostelic, likewise SujUJaria vasmJaris and S. 

 2ndcherrima had iDrotostelic axes, wliile on tlic otlior liand S. dipJoxylon, S. (']c<j((ii><, and 

 S. sjrhmlosa had sijihonostelic axes ; a similar relation exists between Sehujludla VKirtcnsil 

 and *S'. lueci(j(it<i. In other instances diifcrent genera of the same natural order may exem- 

 plify the two types of stelar structure c. r/., in the Gleicheniaceae, Gleichenia is protostelic 

 and Platyzoma is siphonostelic. Similar exam2)les are afforded by the Hymeno2)hyllaceae 

 and Schizeaceae. 



The Ancestors of tjie E(iUisETACEAE. 



In this connection the question may properly- T)e asked where are the pi'otostelic 

 Equisetales to be found. The Splienophyllales immediately suggest themselves in reply to 

 this question. Stur {op. cif., p. 17) and Rothpletz (Botanisches centralblatt, Gratis 

 beilage 3, pi. 11), have both called attention to their remarkable external resendjlance to 

 Archaeocalaniites in their strobloid fructifications, their rigid and articulated stems, and 

 whoiied superposed dichotomous leaves; The branches of the Sphenophylliiles also 

 resembled those of the Equisetales in rising at the nodes, between the leaves (Renault, oj). 

 cit., texte, ]). 170). Solms-Laubach {op. cif.) has described the sporangiophores of liow- 

 manites rbmeri as peltate and Scott {^op. cit., 1897, B.) has compared the much more com- 

 plex sporophylls of Cheirostrobus with those of the calamitean Palaeostachya, and makes 

 the important suggestion that the comparison of the cone of the Equisetales with that of 

 Cheirostrobus is likely to change considerably our views of the morphology of the former. 

 He probal)ly has in mind the extension of the comparison to Calamostachys, Paracalamo- 

 stachys, Cingularia, etc., where the sporangiophore does not immediately suggest itself as 

 the ventral segment of the sporophyll, as it does in Palaeostachya. Even in' the latter 

 genus the sporangiophore more often as in the case of the sporangiiun of the li\ing Sela- 

 ginella (Goebel, Bot. zeit., 1881, p. 697; Bower, Phil, trans. Yoy. soc, 1894, B., -^. 523), 

 appears to originate from the axis than from the ventral surface of the dorsal sterile seg- 

 ments. Weiss (Steinkohlen-Calamarien, Heft 2, p. 7) has pointed out that it is jwssible 

 to arrange a series of calamitean cones, starting with forms which have the sporangio2:)hore 

 attached to the base of the dorsal segment, and ending with those which have it high up 

 on the axis. It is interesting to note in this connection, that the nmnber of vascular 

 bundles in the axis of all calamitean cones yet examined is not greater than the num))er 

 of sporangiophores, Avhile the so-called sterile leaves are frequently twice as numerous as 

 the vascular strands and consecjuently as tlie sporangiophores (Calamostachys) . This 

 feature, together witli the fact that the sporangiophores were placed aljove and between 

 the members of the reduplicated sterile whorl, and the fact that the nodes correspond in 



