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PROFESSOR A. ANSTRUTHER LAWSON ON 
Fig. 28. This represents a median section through a very young antheridium. There are three or four 
wall cells and two inner cells. This is the youngest stage of the antheridium found. The inner cells are 
conspicuous by the dense granular cytoplasm and the large deeply staining nuclei, x 290. 
Fig. 29. This figure also represents a median section through a young antheridium, but a stage in the 
development slightly in advance of that shown in the preceding figure. The inner cells have divided, and 
we thus have the four-celled stage. x 290. 
Fig. 30. This is a representation of a slightly older stage in the development of the antheridium as 
seen in median section. The wall cells have evidently increased in number, as also have the inner cells. 
This is no doubt the eight-celled stage. x 290. 
Fig. 31. This figure represents a median section through a young antheridium. It is a stage in the develop- 
ment slightly in advance of that shown in fig. 30. It is the sixteen-celled stage of the inner cells. x 290. 
Fig. 32. This figure also represents a young antheridium in median section. It is a stage in develop- 
ment following immediately on that shown in the preceding figure. It is the thirty-two-cell stage of the 
antheridium. x 290. 
Fig. 33. A representation of a median section of a nearly mature antheridium. The nuclei of the 
spermatocytes have undergone a change. They have become crescent-shaped or slightly coiled deeply 
staining bodies. They are the immature spermatozoids. x 290. 
Fig. 34. This represents a mature antheridium as seen from the surface. Only the wall cells are repre- 
sented, and the arrangement of these into a large almost spherical structure is very characteristic, x 290. 
Fig, 35. This figure shows a tangential section through a mature antheridium. The mature coiled 
deeply staining spermatozoids are clearly visible. x 290. 
Fig. 36. This figure represents a few immature spermatozoids taken from the antheridium shown in 
fig. 33, but more highly magnified. It will be seen that the nucleus becomes crescent-shaped and then 
coiled, and stains very deeply with saffranin. x 900. 
Fig. 37. This represents several mature spermatozoids taken from the antheridium represented in 
fig. 35, but much more highly magnified. The coiled and multiciliate nature of these gametes is clearly 
indicated. x 900. 
Fig. 38. This figure represents an archegonium from a section that was not quite median. There are 
shown six tiers of cells in the neck and the venter containing the egg cell below the surface, x 290. 
Fig. 39. This represents a median section through, the archegonium. It shows a distinct egg cell in 
the venter, a straight neck of six tiers of cells, and two nuclei in the neck canal. x 290. 
Fig. 40. This figure represents an archegonium as seen from above. There are four cell rows which 
enclose a channel occupied by the neck canal cell. x 290. 
Fig. 41. This represents a median section through a mature archegonium. The large deeply staining 
egg nucleus is a conspicuous feature of the venter. The distal tiers of the neck ce'lls are broken away, 
leaving only two tiers. This archegonium is ready for fertilisation. x 290. 
Fig. 42. This figure represents a stage similar to that shown in fig. 41, but it also shows a variation in 
the number of tiers of neck cells that are left after the breaking away of the distal tiers. Here it is clearly 
shown that there are three left. In fig. 41 there were two, and in fig. 43 there is but one. x 290. 
Fig. 43. A median section through a mature archegonium at the time of fertilisation. The venter with' 
its conspicuous egg nucleus and cytoplasm and the remaining tier of neck cells are represented. There are 
also to be seen deeply staining coiled structures that I interpret to be spermatozoids at the entry of the 
neck canal. x 290. 
LITERATURE CITED. 
Bertrand, C. Eg., “Recherches sur les Tmesipteridees,” Archives botaniques du N or d de la France, Lille, 
1881-3. 
Bertrand, C. Eg., “Le type Tmesipterid^e,” Bull, de la Soc. Bot. de France, Lille, t. xxx, Paris, 1883. 
Bertrand, C. Eg., “Note sur la nature morphologique des rameaux aeriens des Psilotums adultes,” Bull, de 
la Soc. Bot. de France, 1883. 
