THE ANCIENT FERNS 



of both generations from this region. Since the prothalh have not, so far as I am 

 aware, been described previously from England, though they have doubtless been 

 found by other workers, it may perhaps be of interest to give some biological notes 



about them. 



Prothalh of 0. vulgatum (Fig. 264) were found by me on many occasions in the summer 

 of 1 94 1 between the months of May and September in a field near Adlington in Che- 

 shire, which had been long under grass and from which turf had been cut a few weeks 

 before the search began. Attention had been attracted to the field by the circumstance 

 that young Ophioglossum fronds with severed petioles were found in the cut turf which had 

 been laid as a lawn in a neighbouring garden. When the site of the cutting was visited 







S 



. «t. ^ 





r 



• » 



Fig. 262. Meiosis in British Ophioglossum in balsam after acetocarmine. x 1000. For explanatory 

 diagrams see Fig. 263. a. O. liisitanicum L. b. 0. vulgatum L. 



some fully expanded fertile fronds of Ophioglossum were found to be growing in the un- 

 disturbed grass at the edge of the bared patch. Study of the rest of the field showed that 

 local small colonies of the fern were scattered about in various parts, too far away from 

 each other to be easily the result of passive vegetative expansion by means of the root 

 buds, and the possibility of inoculation having occurred by germinated spores seemed 

 favourable. To search for these, sods of the soil from which the turf had been removed 

 were dug out from the immediate neighbourhood of the untouched adult plants and 

 carefully crumbled to pieces over a sheet of white paper. As it turned out, prothalh 

 were detected surprisingly easily, in most cases at a depth corresponding to about 5 in. 

 below what must have been the original surface of the grass before the turf had been 

 removed. 



The prothalh of Ophioglossum are little, contorted, wormlike objects, very like those of 

 Psilotum referred to in Chapter 14, though without any trace of vascular tissue. A group 



264 



