558 
Sinnott and Bailey . — The Origin and 
anatomy of such a wide range of plants, together with the other objections 
which we have cited, must be regarded as casting considerable doubt on 
its truth. 
If this hypothesis is to be rejected, however, we must endeavour 
to construct one in its place which shall explain the facts before us more 
satisfactorily and indicate clearly how the transition from woody plants 
to herbs, which we believe to have taken place, has been brought 
about. 
In the first place, the type of herbaceous stem which possesses many 
distinct bundles, although somewhat more frequent than any other con- 
dition, cannot at all be regarded as ‘ typical * for all herbs. Many genera 
and often whole families possess vascular cylinders which are continuous and 
unbroken. The Caryophyllaceae, Phytolaccaceae, Hypericaceae, Lythraceae, 
Onagraceae, Ericaceae, and Polemoniaceae may be cited as families in 
which practically all the herbaceous forms are characterized by such 
a solid ring of primary and secondary wood. In many other families there 
are numerous genera where the stem is of this type. It is worthy of note 
that in all such cases the twigs of related woody forms show in the same 
way a practically unbroken primary ring and an absence of very wide rays 
in the secondary wood. The herbaceous stem, therefore, is essentially the 
first annual ring of the corresponding woody form, with a reduced amount 
of secondary growth. The manner in which such an herbaceous stem has 
arisen is indicated in Diagrams 5 and 6 ; and in PI. XXXIX, Figs. 3 and 
4, 5 and 6, and 8 and 9. 
In the case of the many-bundled herbaceous stems we have already 
noted the resemblance which the interfascicular parenchyma, in less reduced 
forms, bears to the broad medullary ray of woody plants. The first annual 
ring of Fagus (PI. XXXIX, Fig. 2), for example, resembles rather closely 
certain of the stouter herbaceous stems. In a paper contemporaneous with 
this, the writers (3) bring forward evidence in favour of the theory that the 
wide ray of Angiosperms has had its origin not in a process of ‘ compounding 9 
or gradual conversion of vertical tracheides into radial parenchyma, but by 
a simple increase in width of the' primitive uniseriate ray. This widening 
of the rays is especially apt to occur opposite the gaps in the primary 
cylinder and causes these gaps to become wider and longer, thus ‘ localiz- 
ing’ the primary wood even in many woody plants. In the development 
of the multifasciculate herbaceous type, these rays usually increase still more 
in width and become the interfascicular parenchyma. Cambial activity 
tends to become much reduced within them or to disappear there altogether. 
Such a condition is characteristic of the softer herbaceous stems of Dicotyle- 
dons and probably formed the basis on which has been built up the typical 
stem of the Monocotyledons, which seems clearly to have been primitively 
herbaceous. The origin of such a many-bundled herbaceous stem from 
