THK EMBRVd 



141 



Angiopteris (Farmer I). The root initial now divides by regular segmentation and 

 the root apex pushes rapidly down through the underlying foot and ultimately 

 emerges on the lower side of the prothaUium. In the meantime the cotyledon grows 

 actively and there is a rapid elongation of the whole embryo in a vertical direction. 

 As in the case of Marattia, it is difficult to prove that the cotyledon grows from a 

 single initial cell. The cotyledon has very much the form of that in Marattia, 

 growth being more active on the outer side, so that it curves over the stem apex 

 very much as the cotyledon does in the embryo oi Botrychium virginianum. About 

 the time that the cotyledon is ready to emerge, the apex becomes flattened out and 

 (sometimes, at any rate) there is a true dichotomy of this apex (see fig. 112, B). 



In the primary root there seems to be no question of the presence of the single 

 initial cell which, at first at least, has the tetrahedral form, but later on is apt to 

 have the base truncate, although it usually has three series of lateral segments. 

 I have not been able to confirm Farmer's statements that the single apical cell is 

 later replaced by a group of similar initials, as in the later roots of the sporophyte, 

 although it is not at all impossible that such may sometimes be the case. The 

 development of the embryo of the vascular bundles in the young sporophyte is 

 exactly the same as in the corresponding stages of the embryo in Marattia. 



THE EMBRYO OF KAULFUSSIA. 



So far as I am aware, no account has been published of the embryo in Kaul- 

 fussia, except one of my own (Campbell 1 1). Only two young embryos were found, 

 so that it was impossible to follow in detail the early history of the young sporophyte. 

 The basal wall, as in the other Marattiaceae, is transverse and, to judge from a 

 comparison of similar stages of the embryo in Marattia and Angiopteris, all of the 

 organs of the young sporophyte in Kaulfussia, except the foot, are also of epibasal 

 origin. Figure 113, A, shows a nearly median longitudinal section of the young 

 embryo. This is very much elongated transversely, and to judge from the position 

 of the cells the basal wall is probably followed by the median walls, forming nearly 

 equal quadrants. The large cell (jf) in one of the epibasal quadrants corresponds 

 in position to the similar cell found in the embryos of the other genera and very 

 likely may represent the primary initial cell of the stem. The embryos, however. 



Fig. 113. — Young embryos of A'awZ/wji/a. X275. 



A. Longitudinal section. 



B. Three cross-sections of a similar embryo, h b, basal wall; 11, quadrant wall. 



were too young to make clear the relation of the cotyledon and primary root to the 

 stem. Three nearly transverse sections of an embryo of about the same age are 

 shown in fig. 113, B. To judge from the structure of the older sporophyte at the 

 time when it first emerges from the prothalHum, Kaulfussia agrees in the main with 

 Marattia and Angiopteris in the origin of the young organs of the sporophyte. 



