( Intraxylary) Phloem in the Stems of Dicotyledons. I. 571 
merely a matter of terminology as to whether such a bundle (the bicol¬ 
lateral) must be regarded as two bundles lying side by side, of which 
one has developed phloem only, or whether the bundle must be called 
bicollateral; the nature of the bundle is not thereby changed. I do not see 
why it should not be called bicollateral, as this better expresses the single 
character of the strand ; the development shows that the second phloem 
belongs to the normal bundle.’ 
Col states that their masked origin and rapidity of formation has led 
to the Cucurbitaceous bundles being passed as bicollateral. 
Original Observations. 
Preliminary Remarks. 
As a result of his previous anatomical investigations in other plants, 
the writer has long been convinced that, in order to discover data which 
may throw light on the origin and meaning of an anatomical structure 
of doubtful interpretation occurring in the vegetative shoot, it is generally 
useless to study this latter from the point of view of its developmental data, 
whether culled from the seedling stem (either in its epi- or hypocotyledonary 
regions) or from the apical meristem of the adult stem. For these data 
are likely to throw a minimum of light, or none at all, on the nature of 
a doubtful structure ; on the contrary, they are often very misleading . 1 
The conviction, on the other hand, was reached that a far more use¬ 
ful mine of information lay in a study of the mature stem, and especially 
of the more conservative organs of the plant, such as the peduncle 
and the various appendages of the reproductive axis, as also the foliage- 
leaf. These organs, having undergone less modification in the course of 
evolution of the plant as a whole, are likely to exhibit in their structure 
more ancestral features, and to reveal the particular character, whose 
morphological value it is desired to estimate, in a form nearer to that from 
which it originally sprang than can possibly be the case in the vegetative 
axis. 
All these conclusions, previously arrived at, have been confirmed 
as a result of endeavours to throw light on the origin of the internal 
phloem in Cucurbitaceae, as will be seen from what will now be brought 
forward. In one or two cases, however, it will be noted that a study of 
the vegetative stem affords most of the necessary data, as in Acantho- 
sicyos and Ecballium. Brief accounts of seedling structure are given 
in one or two instances, more for the sake of completeness than 
anything else. 
1 H^rail’s reliance on the position and mode of ontogeny of the internal phloem is, from the 
morphological view-point, entirely useless. 
