BY T. WHITELEOOE. ' 561 



and to Mr. Allan R. McCuUoch for the completed drawings which 

 illustrate this paper; also to Mastei- Bert Deo,otardi for valuable 

 aid in the search for plants of Tmesipteris and fruiting-speciniens 

 of Psilotuni. 



Measur(Mnents of spores, and reproductive organs (jf Psi/o/m)/. 



Male spore. — Length, 0-00 to ()-08 mm. ; breadth, O-OM to 

 00^ 111111.; antheridial cells, O'OIS to 0"04 mm. Antherozoids as 

 seen i/i .•^ifn, average diametei-, O'OO-'J mm. 



Female sjwre. — Length, O-Ofi to 0-OS mm. ; breadth, ()-027 to 

 0-03 mm. Unfertilised gametophyte, ()■i)'^ to 0-04 mm. in dia- 

 meter. Fertilised gametophyte, 0'04 to 0*08 mm. in diameter. 



Additional Xotp. — Several months have elapsed since the pub- 

 lished notice of the slides exhilnted at the Meeting of the Society 

 in Ajiril last, and since the foregoing paper was completed. 

 During the interval, much time has been devoted to a fiirther 

 study of mounted slides, and examples preserved in formalin. 

 The results have exceeded \n\ expectations. Many doubtful 

 points have been cleared up, and some new phases of development 

 observed. 



The male spore produces eight or more antheridia; as many as 

 twelve, in one instance, have been seen. When near maturity, 

 the antheridia emerge from the ventral slit, as pear- or comma- 

 shaped bodies, the cell-wall being thin and plastic; before the 

 antherozoids are mature, the wall becomes consolidated, and the 

 cell assumes a globular form. Tn many cases, the last one or two 

 cells do not completely emerge, but remain deeply imbedded in 

 the spore. So far, no traces of any cell or cells have been found, 

 which might be regarded as a prothallus, either rudimentary or 

 otherwise. 



The female gametophyte emerges from the ventral slit as a 

 small, thick- walled vesicle. It is situated in the centre of the 

 nearly straight border, and is drop-like in outline. Structural 

 details are difficult to see, until it has attained a diameter of 

 about 0-015 mm. It is then seen to be a multicellular bjsdy, 



44 



L i J R A R Y 



