THE ANCIENT FERNS 



series on the number 8, very familiar in the flowering plants though not so far en- 

 countered in the ferns ; in that case we might either 

 hope to find, or could postulate the former exis- 

 tence of, species with the intermediate numbers 8, 

 1 6, 32, 64. If, on the other hand, the correct 

 numbers for the British species are 126 and 252 

 respectively, we have an extension of the position 

 already encountered in Cystopteris, in which the 

 immediate monoploid number was 42, though this 

 might in turn be referable back to a basic haploid 

 of 7. Since present accuracy does not enable us 

 to distinguish between these two possibilities, we 

 must leave the matter sub judice at this point. It is 

 evident, however, that the two British species of 

 Ophioglossum have opened up some very interesting 

 problems in a very interesting genus which could 

 profitably be further pursued in other parts of the 

 world. 



In comparison with Ophioglossum, the one British 

 species of Botrychium (Fig. 267) offers little of 

 special interest from a cytological point of view. 

 From the technician's standpoint it is more 

 difficult to handle than Ophioglossum, in that its 

 seasonal periodicity is less convenient. In both 

 species of Ophioglossum meiosis takes place when 

 the fertile fronds are well above the ground and 

 the sporangia easily seen and tested. In 0. vul- 

 gatum itself the fertile spike is then about 2 cm. 

 long, and the month in the north of England is 

 June. The Moonwort, Botrychium lunaria (L.) Sw., 

 matures its spores much earlier when the fronds 

 are in the act of piercing the ground and whilst the 

 sporangia are still closely enveloped by the unex- 

 panded sterile portion. This means that they are 

 very difficult indeed to find in the wild until 

 they are too old, unless very exact knowledge of 

 localities has been assembled in a previous year. 

 On the other hand, cultivation presents difficulties, 

 but under suitable conditions sods containing 

 plants can be maintained alive through at least 

 one season, and this, in my experience, is the less 

 difficult way of obtaining fixations. 



Figs. 268 and 269 show meiosis in material of 

 B. lunaria obtained from Teesdale in summer but 



Fig. 267. Botrychium lunaria (L.) Sw. 

 from Teesdale. Natural size. 



269 



