1921] WALKER—GAMETOPHYTES OF EQUISETUM 385 
gonia, which are usually conspicuous, and in such cases no traces 
of antheridia could be found. 
In general it seems that the thallus continues to grow, forming 
new sex organs until sporophytes have developed to such an extent 
that the tissues are exhausted. If a sporophyte starts when the 
thallus is small, one rarely finds young sex organs developing later. 
If, however, fertilization does not occur, the archegonia dry up 
and new ones, and often antheridia also, are formed until fertiliza- 
tion is accomplished. If the thallus has attained considerable size 
before any fertilization occurs, a large number of sporophytes may 
be supported by it without injury, and in such cases the develop- 
ment of sex organs may continue until many archegonia have been 
formed and fertilized, and until the sporophytes are well advanced. 
The sporophytes invariably occur near the periphery, as shown in 
figs. 4, 7, 9, 10, and 11 of the thallus, while old functionless 
archegonia often show between the branches entirely across the 
surface, 
The younger sporophytes are nearer the edge of the disk, and 
the active archegonia and antheridia are in the peripheral meristem 
(figs. 8, 9, r2-19, and text figs. 2, 3). Eleven sporophytes in 
early stages have been seen on one gametophyte, but not more than 
seven have been found sufficiently large to be seen by the unaided 
eye. In a few cases dead young sporophytes were observed, but 
in the majority of cases they looked in good condition. As the 
growing season was nearing its close, however, it is hardly probable 
that sporophytes not yet having secured a foothold in the ground 
could mature. 
Biscuorr, according to BUCHTIEN (1), reported finding monoe- 
cious gametophytes of E. sylvaticum bearing archegonia on their 
older parts and antheridia on the younger parts, and stated that 
monoecious gametophytes are not so rare as commonly believed. 
He found them occasionally in all his cultures. He also found the 
gametophytes of E. sylvaticum to be largely male, but many bore 
archegonia, and among these a comparatively large percentage 
bore antheridia also. He considered that the antheridia were 
formed after archegonia ceased to develop, but some bore them on 
different parts of the spreading meristem at the same time. 
