490 OPHIOGLOSSALES 



Bruchmann to the hypobasal hemisphere in O. vulgatum, but to the epi- 

 basal by Jeffrey in B. virginianum, where the whole hypobasal hemisphere 

 goes to form the foot. In B. Lunaria Bruchmann found it impossible 

 to refer it with any certainty to either. These facts, taken together with 

 a similar uncertainty in the embryos of Equisetnm, and the demonstration 

 in the Lycopods that the root is variable in its point of origin, show 

 that its indeterminate position is a frequent feature in the embryos of 

 the strobiloid Pteridophytes, however constant it may appear to be in 

 -the Ferns. 



Regarded as a whole, the Ophioglossaceous embryos without suspensor 

 consist of a simple shoot, of which the polarity becomes apparent relatively 

 late, but it is of the same nature as that seen in Isoe/es, in Eqnisetum, 

 and in the Ferns. The apex of the axis, arising in close relation to the 

 intersection of the epibasal octant walls, is directed to the neck of the 

 archegonium : the foot occupies the opposite pole, and the root appears 

 as a lateral, accessory part, of indeterminate position, but of relatively 

 early origin, and precocious growth. 



The other type of embryogeny seen in B. obliquum shows an exactly 

 inverted polarity : the condition appears to be comparable to that of the 

 Lycopodiales (excl. Isoetes] : the pole directed towards the neck of the 

 archegonium becomes the suspensor. while the opposite pole develops 

 the embryo, having parts quite comparable in position to those, for 

 instance, of Selaginella spimilosa?- but with an early and strong assertion 

 of the first root. The importance of this lies in the relaxation which 

 such a fact brings from any rigid view of embryonic development : it 

 seems completely to disprove any morphological predestination attaching 

 to the primary cleavages of the zygote in the Pteridophytes. 



The materials of this discussion may now be drawn together into a 

 general hypothesis of the morphology of the sporophyte, as it is seen in 

 the Ophioglossaceae. At the outset it has been concluded that the some- 

 what inconstant occurrence of mycorhiza in the sporophyte is not a sufficient 

 reason for assuming that the family has undergone general reduction : in 

 the absence of any such preconception the family may be treated com- 

 paratively as an ascending series, though with the recognition of occasional 

 reduction. The facts before us are in accord with the following account 

 of it. The embryo sporophyte achieves an early polarity, marked by the 

 definition of the stem-apex : the base of the shoot thus initiated is 

 represented by the foot, or in B. obliquum by the suspensor. The 

 primary axis thus defined continues its growth, with rare bifurcation, 

 throughout the life of the stock ; but adventitious or axillary buds (usually 

 arrested) may be formed, which simply repeat the development of the 

 primary shoot. The axis bears leaves in spiral or dorsiventral succession, 

 and they are all of one primitive type, though liable to differentiation. 



1 Compare Bruchmann, /.<., Taf. iii., Fig. 63. 



