572 Lang. — On a Prothallus pr ovisionally referred to P silo him. 
The prothallus was almost certainly completely embedded among the 
adventitious roots, although, since some of the latter had been removed 
before it was noticed, this was not directly observed. Its general form will 
be evident from Figs, i and 3, which represent two views of the uninjured 
prothallus magnified seven times. Its natural size was about one quarter 
of an inch in length by three-sixteenths of an inch across at the upper end, 
which was the widest part. As the figures show, it was approximately 
cylindrical, agreeing in general form and symmetry with the prothalli of 
some species of Lycopodium. As in these, a lower vegetative region could 
be distinguished from an upper one, to which the sexual organs were con- 
fined. The vegetative region, which formed the larger portion of the pro- 
thallus, was of a brown colour and thickly clothed with rhizoids. Below, 
and somewhat to one side, it narrowed into a conical end, the relation of 
which to the general body of the prothallus at once suggests a comparison 
with the primary tubercle, which is more or less clearly distinguishable in 
most prothalli of Lycopodium. The upper portion of the prothallus con- 
sisted of a somewhat depressed central area and a thick overhanging 
margin, in which numerous antheridia were present. A comparison of 
Fig. 3, which represents a section through the whole prothallus, with 
Fig. 4, in which the overhanging margin is better seen, will make the 
relation of these parts clear without further description. It is sufficient 
to point out that, as in most types of Lycopodium prothalli, this prothallus 
is differentiated into a primary tubercle, a vegetative region, and a sexual 
region. There was clearly no apical growth, and, as will be shown below, 
the zone intervening between the vegetative and sexual regions must be 
regarded as the meristematic region. The fact that the sexual organs were 
confined to the margin of the sexual region indicates that the prothallus 
was a relatively old one. A comparison with prothalli of various ages of 
e. g. Lycopodium clavatum 1 makes the manner in which the existing relation 
of parts would follow from one in which the whole summit of the prothallus 
was covered with sexual organs perfectly clear. 
There was no trace of the existence of any assimilating lobes such as 
occur among the sexual organs of Lycopodium cernuum. When fresh the 
upper portion of the prothallus had a faintly green tint, but examination 
on the spot did not reveal any chlorophyll corpuscles, nor could any be 
detected on more careful examination later. It is therefore probable that 
the prothallus was not exposed to light, and was incapable of independent 
assimilation. 
The structure of the several regions of the prothallus must now be 
described in detail. The most convenient order in which to take them will 
be the sexual region, the vegetative region with the primary tubercle, and 
1 Bruchmann, Ueber die Prothallien und die Keimpflanzen mehrerer europaischer Lycopodien. 
Gotha, 1898. Cf. Taf. 3, Fig. 1, with the series of prothalli of various ages on Taf, 1. 
