HALLE, ON THK SPORANGIA OF SOME MESOZOIC FKRNS. 17 



show some of the best examples. Tlie aniiuhis consists of 

 about 30 cells on an average. It appears to continue all round 

 the sporangium, Avliich in the specimens figured has a fairly 

 regular circular outline in its flattened state. On a closer 

 examination, however, it is seen that the annulus is not con- 

 tinuous but open at one place. In figs. 14 — 16 the gap is 

 in the lower parts of the figures. At the break the two ends 

 come very close to each other, or even overlap, but they do not 

 meet and clearly lie in different planes. This feature is not 

 very well shown in the photographs, but in the actual spe- 

 cimens it can be clearly observed by changing the focussing. 



The annulus is thus incomplete and twisted, but continues 

 practically all round the sporangium. It is probably this 

 feature that has caused the difference of opinion as to whether 

 the annulus is comi^lete or incomplete. Owing to its sinuous 

 course it is very rarely that the whole annulus can be seen 

 from one side. 



The sporangia that show the whole annulus have always 

 a circular outline and it may be inferred from this that the 

 original shape of the sporangium was either globular or len- 

 ticular. When the sj^orangium is seen parallel to the plane 

 of the annulus, it is found to be only a little broader than the 

 latter; and it is therefore more probable that the actual shape 

 was lenticular rather than globular. There is no trace of a 

 stalk, and it is impossible to make out the orientation of the 

 annulus in respect to the apex and the base of the sporangium. 

 It would seem probable that the annulus was more or less 

 vertical, but there is no direct information on this point. 



The sporangia of DictyophyUum are strikingly large in 

 comparison with those of the recent ferns with which it has 

 bceu compared. I have found the diameter of the annulus 

 to be 0,5 — 0,6 mm. Nathorst gives the size of the sporangia 

 as 0,4 — 0,6 mm. The sporangia of Dipteris are stated by 

 Seward & Dale (1001, p. 500) to measure 0,o2 mm. in length. 

 This figure quoted also by Nathorst (1906, p. 19) is evidently 

 a misprint for 0,2 mm. Yet the difference between Dictyo- 

 phyllnm and Dipteris in this respect is considerable and sug- 

 gested an examination of the spore-output })er sporangium 

 in DiriyophyUum. The sporangia can be easily lemovcul in- 

 dividually from the matrix. On treatment with Sciiultze's 

 luixture and ammonia the spores of each sponuigiuiii usually 



Arkif für botanik: Band 17. No t. 2 



