540 Bower.—On the Primary Xylem , and the 
disposition of its weak vascular system on the Ophioglossaceous plan, and 
with the endodermis variable in clearness of characters. Endodermal 
markings were seen outside the meristeles and also in the pith, in positions 
generally corresponding with what is shown in Poirault’s drawing of 
O. Bergianum. Further, the outgoing leaf-trace was in some cases sur¬ 
rounded by a special endodermis of its own. as will be shown to be the case 
in Botrychium . These conditions are perfectly compatible with the arrange¬ 
ments more clearly seen in Botrychium , which will be described below. 
The conclusion which I draw from these imperfect observations is, that 
Poirault’s observations are to be upheld ; further, that the small species of 
Ophioglossum which show, however inconstantly, an internal endodermis, 
repeat on a reduced and incomplete scale the same type of structure as is 
seen more fully developed in Botrychium . It will be desirable that this be 
tested by some observer with more ample material at his disposal. 
A similar variability to that found in the genus Ophioglossum in 
respect of the medullation of the individual in the young state, is seen 
also within the genus Botrychium. Already Jeffrey has shown that in 
B. virginianum the sporeling is medullated from the first, a fact which is 
probably in relation to its nutrition by the large storage prothallus, which 
serves as an effective nursing mother (loc. cit., pp. 31-2). The fact is 
corroborated by sections of my own sporelings collected in Jamaica. No 
internal endodermis was seen in them. In order to compare with this 
the sporeling structure in B. Lunaria , and at the same time to give the 
most pointed antithesis by selecting weak plants instead of those highly 
nourished by large storage prothalli, serial sections were cut from sporeling 
plants taken from the rocky ledges of the Breadalbane Hills, about 3,000 
feet up. The plant most exhaustively treated bore one leaf, with a spike 
on which were only four sporangia. The axis was about \ inch in length, 
and very thin, with several roots. As sections showed, a number of 
leaves had preceded that which was expanded. Following the series of 
sections of this plant from below upwards, the stele appears from the first 
to be composed of tracheides with occasional parenchyma cells intermixed, 
while it is circumscribed by an endodermis, which is well defined con¬ 
siderably below the point of departure of the first leaf-trace (PI. XLV, Fig. 6). 
Three roots were attached at this region. Already the cells around the 
primary xylem show activity of division, thus initiating the secondary de¬ 
velopment. At first the parenchyma cells in the xylem are not located 
specially at the centre of the stele ; but as the level of departure of the 
first leaf-trace is approached, a concentration of the parenchyma occurs 
internally, and a central pith is thus formed. An essential point is that 
intraxylic parenchyma exists before the appearance of a definite pith, and 
contributes to its formation. Very soon the pith is put in connexion with 
the outer conjunctive tissue by the opening of the xylem-ring. This 
