574 Wars dell .— The Origin and Meaning of Medullary 
some cases, of a small inverted bundle with the internal-phloem group. 
This phenomenon will be referred to hereafter in the case of another 
plant, and will then be commented on, as it is a fact of first importance. 
In the basal region of the peduncle the ring of bundles is quite normal, 
and none of the small bundles occur. 
Cucurbita Pepo. 
Seedling. 
The transition to root-structure occurs just below the ‘ heel ’. As the 
protoxylem of each bundle divides and turns outwards, portions of the 
internal-phloem strand also branch off on either side and pass out to unite 
with the external phloem ; this is easily observed, as the albuminous cells 
are particularly abundant and well-defined. This £ passing out ’ of the 
internal phloem is deduced from the fact that at this level connexions 
between the internal and external phloem occur, which phenomenon is not 
present above and below this region, and that the internal phloem decreases 
greatly in amount at a lower level. There would not occur the above- 
mentioned connexions of the external with the internal phloem if the latter 
merely died out in situ. The connexions, consisting of groups of albuminous 
cells in the rays between the bundles, therefore indicate a passing out 
of a portion of the internal phloem. Now, it is an interesting fact that not 
all the internal phloem passes out. The protoxylems revolve, and a 
continuous cylinder of wood is formed before the latter process is complete ; 
so that scattered elements of internal phloem are left behind and enclosed 
in the wide pith, and eventually die out below. The conclusions of 
Lamounette and Fischer are thus only very partially correct in regard 
to this genus. The former relied far too much on the misleading data 
of the ontogeny. 
Stem . 
In the subaerial portion, some distance beyond the yellow-coloured 
underground part, the cambium of the internal phloem has, in most of 
the bundles of the ring, developed a large amount of xylem which 
consists mainly of parenchyma, with vessels and fibres in some of the 
bundles. The phloem of these bundles is connected with that of the 
ring-bundles by commissural strands ; the woody part of the xylem ap¬ 
pears to die out at a lower level, to reappear again in the yellow under¬ 
ground portion. 
In another plant, at the lowest node, a few inches above the base 
of the stem, where the yellow portion of the latter begins, the internal- 
phloem groups send off branches abundantly both to the external phloem 
