THE GAMETOPHYTE GENERATION OF THE PSILOTACE^. 
105 
In such mature antheridia— and they were frequently found — it is comparatively 
easy to follow the general transformation of the spermatocytes into coiled spermato- 
zoids when one uses a high-power, oil-immersion lens. In fig. 36 several of the 
spermatocytes are represented. The nuclear substance has become a very dense 
coiled, or slightly spiral tapering filament, occupying the periphery of the cell. The 
cytoplasm appears as a vesicle within the coils of the nucleus. The vesicle, like the 
cytoplasm, is not a feature of the mature gametes. As indicated in fig. 37, these 
bodies are multiciliate, and their characteristic appearance at maturity is here 
shown. I unfortunately was unable to find this corresponding stage for Tmesipteris. 
A comparison of the size of the two spermatozoids should prove interesting in view 
of the difference in size of the cells in the earlier stages. 
The Archegonia. 
In the case of Tmesipteris , as J have stated above, the archegonia were of more 
frequent occurrence than the antheridia. Just the reverse is the rule with Psilotum. 
At least, that is true if the prothalli studied may be taken as fair samples. In every 
prothallus of Psilotum observed, the antheridia appeared in much greater numbers 
than the archegonia. But, as in Tmesipteris, these latter organs develop from all 
sides. They appear on every surface quite indiscriminately among the rhizoids and 
antheridia. Compared further with Tmesipteris, there is one other point of difference, 
which, although perhaps of no great importance, is quite obvious. In Tmesipteris 
I pointed out that the archegonia nearly always appear in crowded masses (fig. 2). 
I have never observed this in Psilotum. These organs as a rule are more scattered, 
and more widely separated from one another. In fig. 24 we have represented the 
surface view of a young prothallus, and the manner of the distribution of the 
archegonia is shown. Seven archegonia may here be seen widely separated from one 
another. In fig. 18, twelve of these organs may be seen widely distributed over the 
prothallus. This may be observed even to better advantage in the older prothalli. 
From the view shown in fig. 19 no less than twenty archegonia may be counted. 
In none of these cases is there any tendency to the crowding of these organs which 
appears to be characteristic of Tmesipteris. 
From these figures one may also see quite clearly that the venter of the arche- 
gonium is below the surface of the prothallial tissue, and the neck projects out at 
right angles as a short straight tube. There is no curvature to the neck. In the 
younger stages, as one may see in fig. 24 ( Ar ), the apex of the neck is round or dome- 
shaped ; but in the older conditions one or more tiers of cells break away, and the 
neck as a consequence is shortened and abruptly squared off. 
In the transverse views of the prothalli represented in figs. 26 and 27 the 
archegonia may be studied in longitudinal section. In fig. 26 one may see four such 
sections of archegonia alternating with three antheridia. In fig. 27 there are two 
archegonia represented. In all of these the short straight neck may be seen, and also 
