THE EMBRYO 



37 



pendulum only one of the definitive organs, the root, arises in this way, and this 

 becomes diflFerentiated at a very early period. One of the octants next to the arche- 

 gonium at once becomes the apical cell of the young root. This cell is very soon 

 recognizable by its size and shape, and quickly begins its regular segmentation. 

 The primary cap-cell is soon cut off (fig. 20, D), and from now on the young root 

 is very conspicuous. The octant divisions are very clearly marked in this case, 

 and in section 3, which is the uppermost of the three, the large triangular apical 

 cell of the root is very evident. 



Two types of the embryo were seen in this species. One of these (fig. 21, A) 

 is nearly globular in form; the other (fig. 21, B, C) is elongated. The former looks 

 as if it originated from an embryo in which the basal wall was transverse to the axis 

 of the archegonium; in the other it was probably more or less vertical. It is probable 

 that in the former instance the root initial is one of the epibasal octants, while the 

 whole of the hypobasal portion gives rise to the large foot. In the second type it is 

 difficult to say which half should be considered epibasal and which hypobasal, but, 

 as in the other case, one half may be considered to be root, the other half foot, the 



Fig. 21. — Ophioglossum pendulum. Older embryos. 



A. Vertical longitudinal section; /, foot; r, primary root. 



B. Horizontal section. X75. 



C. Older embryo, with single root. 



D. Embryo with two roots; pr, gametophyte. Shaded region occupied by the mycorrhiza. 



growth of both being nearly in a plane at right angles to that of the archegonium 

 axis, and suggesting the relative positions of cotyledon and foot in the embryo of 

 Ophioglossum moluccanum. 



In form the first type somewhat recalls the embryo of Botrychium virginianum. 

 The whole lower portion, or hypobasal half, forms the very conspicuous foot, while 

 from the epibasal region the primary root is developing, and already the rudiment 

 of the second root is visible. Whether the latter arises directly from the primary 

 root, or whether it arises independently from the second epibasal quadrant, is not 

 quite certain. The cells of the epibasal region are evidently actively growing, having 

 abundant protoplasm and conspicuous nuclei. The cells of the foot are larger and 

 much more transparent. 



The second type of embryo (fig. 21, B, C) resembles very closely the second 

 state of the embryo of Ophioglossum vulgatum, where, as is said by Bruchmann, 

 the embryo is "all root." 



