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OPHIOGLOSSALES 



under side. Hitherto only a preliminary account of this strange anomaly 

 within the genus Botrychium has been published, and it will be necessary 



to await the detailed description which will 

 supply the materials for an exact comparison. 

 But meanwhile Mr. Lyon has most generously 

 lent slides showing not only some advanced 

 stages, but also the earliest stages of embryo- 

 geny, from which the following facts and 

 drawings have been derived. 1 Transverse 

 sections of an embryo corresponding to that in 

 Fig. 264, showed the suspensor (s), cotyledon 

 (c), and apex of the axis (ap] in the relative 

 positions ascribed to them by Lyon, and 

 demonstrated the correctness of his interpre- 

 tation of the longitudinal section (Fig. 265). 

 But what is more important is that sections traversing archegonia, shortly 

 after fertilisation, showed that the zygote, while still undivided, grows 



FIG. 265. 



Embryo of Botrychium obliqumn, in 

 transverse section at the level of the 

 stem -apex (/). cc cotyledon ; -y = sus- 

 pensor. From a preparation lent by H. 

 Lyon. 



FIG. 266. 



Botrychium obliquum. First stages in the embryogeny ; before the first segmentation 

 the zygote grows into an elongated tube (the suspensor), which burrows its way 

 irregularly into the tissue of the prothallus. X 150. From sections lent by H. Lyon. 



into an elongated tube, which takes an irregular course downwards into 

 the tissue of the prothallus (Fig. 266) ; its nucleus settles down to the 



1 Mr Lyon's action in this matter deserves special recognition. When circumstances 

 delayed the completion of his own statement, knowing the importance which the main facts 

 bore in embryological comparison, he forwarded a set of slides to me in Glasgow, with 

 permission to use the facts they showed in whatever way I found necessary. F. O. B. 



, 



