1921] ' WALKER—GAMETOPHYTES OF EQUISETUM 387 
by the three cells. This cell divides transversely and forms an 
antheridium exactly as is the case in the antheridia produced in the 
tissue. This is an interesting interpretation of the development of 
antheridia at the tip of a slender branch. As no such antheridia 
were found in these wild gametophytes, however, it does not apply 
to this case. The antheridia open by the disorganization of the 
entire outer wall as previously mentioned. In E. laevigatum, as 
was found by KasHyaP (7) to be the case in E. debile, antheridia often 
occur between the upright branches in exactly the position charac- 
teristic for archegonia. Figs. 12, 15, 17, and 19 show the beginning 
of these branches between antheridia. 
Embryo 
Embryo sporophytes in all stages, from a few cells to those with 
the third shoot an inchlong, were abundant in most of the collections. 
The development was entirely characteristic of that commonly de- 
scribed for the group (JEFFREY 6, and others) (figs. 9, 11,and text fig.1). 
The number of leaves on the primary shoot varies from three to 
four, and on the second shoot from four to five. Fig. 14 shows a 
very young sporophyte at about the 16-cell stage. In fig. 17 and 
text fig. 2 the sporophyte is still larger, while in fig. 9 the sporophyte 
shows all the body regions well organized. Fig. 11, a section of the 
plant shown at the right in text fig. 1, shows the primary branch well 
developed, with its first whorl of four leaves at the base. Its. root 
emerges from the ventral side of the thallus. In text fig. 1 (at the 
right) part of the periphery of the thallus was cut away at A, 
where the cut surface shows. At the left of the gametophyte to 
the right in text fig. 1 and at the right of fig. 11 is the second shoot 
with several whorls of leaves and with its root emerging below. 
In this specimen the leaves on the second shoot were four in a 
whorl, the same as on the first shoot. In fig. 11 the bud for a third 
shoot shows at B. In text fig. 1 the sporophytes also show four 
leaves on the first shoot. This, however, was not universally true, 
many showing but three leaves (figs. 4, 7, 10). The roots for these 
shoots were well developed and deeply buried in the soil. Plants 
transferred to pots in the greenhouse are still growing vigorously 
(March 1), 
