34 



THE OPHIOGLOSSALES 



II. THE EMBRYO. 



The development of the embryo in the Ophioglossaceae has been more or less 

 completely studied in Ophioglossum pedunculosum, 0. vulgatum, 0. moluccanum, 

 0. pendulum, Botrychium virginianum, B. lunaria, and B. ohltquum (Mettenius 1, 

 Bruchmann 1 and 2, Lang 1, Campbell 8, Jeffrey 1, Lyon 1). 



The first division in the young embryo in all of these is usually approximately 

 transverse, although there may be a good deal of variation in this respect. It is 

 probable that in all cases the primary root, the stem apex, and the foot all arise from 

 the epibasal region. The embryo reaches a very large size before the root emerges 

 from the overlying prothallial tissue and all of the organs of the young sporophyte 

 are very late in developing, so that it is not easy to trace their origin back to the 

 early cell divisions in the young embryo. Much the most conspicuous organ of the 

 young sporophyte is the root, which may reach a very large size and an advanced 

 stage of development before any evidence of the other organs is apparent. Indeed, 

 several roots may be developed before the shoot is established. In Ophioglossum 

 vulgatum and Botrychium lunaria, according to Bruchmann's account, the young 



Fig. i8. — Ophioglossum moluccanum. 



A. An old archegonium. Xi8o. 



B. Two-celled embryo within the archegonium. Xl8o. 



C. Two sections of an older embryo. Xi8o. col, cotyledon; /, foot; r, root. 



sporophyte remains several years under ground before the first green leaf appears 

 above the earth, and it is probable that in Ophioglossum pendulum there is also a 

 long period of underground existence before the first green leaf is developed. In 

 Ophioglossum moluccanum, hov^ever, and in Botrychium virginianum, the first 

 leaf developed is a green foliage leaf, vi^hich grows rapidly and soon appears above 

 the surface of the ground. 



THE EMBRYO OF OPHIOGLOSSUM. 



The first figures that we have of the embryo of Ophioglossum are those of 

 Mettenius, but his figures of the embryo of 0. pedunculosum are not at all satis- 

 factory, although he shows correctly sections of the older sporophyte. Lang figures 

 only one embryo, a somewhat advanced one of 0. pendulum. Bruchmann figures a 

 two-celled stage and a single more advanced embryo of 0. vulgatum, but he describes 

 and figures several stages of the young sporophyte. My own study of Ophioglossum 

 was based mainly upon the development of the embryo in 0. pendulum, where a 



