792 PROFESSOR A. ANSTRUTHER LAWSON ON 



from these figures it seems that the distribution of the archegonia has little if any 

 regularity. When they are produced in the older prothalli they are quite numerous 

 and set closely together. 



Fig. 12 is a representation of a more highly magnified view showing four 

 archegonia as they appear in a surface aspect. This figure is instructive, as it shows 

 the relative size of the archegonia to the ordinary vegetative cells of the prothallus 

 and to the rhizoids. It will be observed from this aspect that the opening of the 

 canal is surrounded by four neck cells, and that these neck cells are very much 

 smaller than the ordinary surrounding vegetative cells. At the point where the four 

 neck cells meet there is a distinct opening or canal, and this region in the mature 

 prothalli always took on a deep brown colour. These brown regions were quite 

 helpful, for they indicated the presence of the archegonia from a mere superficial 

 study with the hand lens. 



Before these structures were actually found the bases of old detached rhizoids 

 were at first mistaken for archegonia, but a close study of them with the high- 

 power magnification soon revealed their true nature. The archegonium, as stated 

 above, is a very simple structure. Although unfortunately the very early stages in 

 its development were not found, scores of older ones were, and a study of these makes 

 it clear that in their form and simplicity the archegonia are unique. No evidence of 

 canal cells or of ventral canal cells presented itself ; and while no doubt a more 

 careful future study will reveal these structures, they cannot form a very conspicuous 

 feature. The youngest archegonium found is represented in fig. 13, which was drawn 

 from a median longitudinal section. Here two of the neck cells are shown, and also 

 the egg cell which occupies the central position of the venter. The latter structure, 

 as in all Pteridophytes, is buried in prothallial tissue. The nucleus of the egg cell 

 is clearly shown, occupying a central position in a dense mass of protoplasm. My 

 interpretation of this figure is that it represents a mature archegonium ready for 

 fertilisation, and if canal cells and ventral canal cell were formed they have disin- 

 tegrated and disappeared. Figs. 14 and 15 show two other mature archegonia which 

 have not been fertilised. A great many sections of archegonia of this nature were 

 found, and they all show a distinct peculiarity in the form of the neck cells. In every 

 specimen examined it was found that these neck cells extend very little indeed 

 beyond the surface of the prothallus, and in section they appear as terminating in 

 curiously pointed margins, and these all four together form a flat disc concave in the 

 middle but otherwise parallel with the surface of the prothallus. The concavity of 

 . the disc formed by the four neck cells varied somewhat with the maturity of the 

 archegonium, as shown in the figs. 3 and 12. The shaded portion of the archegonia 

 in fig. 12 is intended to represent the concavity of the neck cells just above the 

 canal. This curious form of the archegonium would suggest an adaptation for the 

 holding of water above the canal and below the overlapping portions of the four neck 

 cells. In the immature stages one would expect>to find these four curious neck cells 



