432 Mr Gregory, Some observations upon 



flicting opinions expressed as to the number of chromosomes in 

 Ferns. 



The work was carried out by means of a stud}' of spore- 

 formation, and by the culture and examination of large numbers 

 of prothallia. 



The results of the cytological examination show 



(1) The number of chromosomes is halved at the division 

 of the spore-mother-cells to form the spores. 



(2) A true reduction (qualitative) division takes place in 

 preparation for the formation of spores 1 . 



Large numbers of prothallia were examined to see whether 

 any might be found to be definitely of one sex Q) only ; material 

 grown from spores taken from several plants of Osmunda regalis 

 was used chieliy, as being the most likely to yield positive results. 

 The prothallia in two pots were mapped for purposes of identifica- 

 tion, and were examined from time to time for a period of nearly 

 two months (May to July ; the spores were sown in February, 

 March and April). Of 142 prothallia so examined 128 ultimately 

 bore archegonia as well as antheridia. The remaining 14 were 

 removed, as supposed males, for cytological examination ; but on 

 cutting five or six no case was found of complete absence of 

 archegonia, which in sections can be recognized in a very early 

 stage. Several hundreds of prothallia grown in pots were 

 examined in the hope of obtaining purely male material for 

 cytological work; but this was so rare that, among those preserved, 

 no undoubted male was obtained. 



A statement has appeared in a text book' 2 to the effect that in 

 Osmunda the spores formed in any one sporangium tend to be all 

 alike, those of certain sporangia giving rise to an excess of males, 

 those of other sporangia to hermaphrodites exclusively. To test 

 this 24 pure sowings were made, great care being taken to ensure 

 that each one contained spores from one sporangium only. The 

 sporangia used were taken from two plants and from different 

 positions (which were recorded) on the fertile spike. No evidence 

 in support of the view was obtained. Some of the cultures 

 became invaded by a fungus, which in four cases obtained a firm 

 hold ; these prothallia were very small, appeared unhealthy and, 

 with one exception, bore no archegonia. In four other cultures 

 fungus appeared to a smaller extent; 51 prothallia were obtained 

 of which 15 bore archegonia as well as antheridia, the remainder 

 bearing antheridia only. 



In the cultures which were clean nearly all the prothallia bore 

 archegonia ; these too did not entirely escape the attacks of the 

 fungus, so that the experiments were abandoned, while a few 



1 Boy. Soc. Proc. Vol. lxxiii., p. 88. 



2 Bennet and Murray, Cryptogamic Botany, Longmans, 1889, p. 66. 



