366 Notes on Recent Literature. 
He criticises the work of Eames and Bailey, justly we think in 
regard to the interpretation of the replacement of narrow rays by a 
broad one in successive annual rings. He also says that the facts 
with regard to the wood of seedlings “ lose their significance if it 
be shown that a similar linking up of small rays to form large ones 
takes place in older parts.” This criticism does not appear valid, 
however, in view of the whole set of facts with regard to the seed¬ 
lings of different groups of oaks accumulated by the American 
authors. According to the theory the “linking up” of uniseriate 
rays would begin in the later formed wood and gradually work back 
during descent into the earlier wood and into the seedling. And it 
is a significant fact that if we take the series: (1) seedlings of white 
oaks, (2) seedlings of black oaks, twigs of evergreen oaks, (3) adult 
wood of deciduous oaks in general, there is a general progression 
in the direction of compounding and the formation of broad rays in 
place of narrow ones. 
Professor Groom also suggests that the linking of rays may 
be of physiological rather than phylogenetic significance. Is 
there any antagonism between the two ? May not physiological 
factors (as indeed the American authors suggest) have been acting 
on the whole in a certain direction during the course of phylogeny, 
and thus brought about a gradual structural change in a corres¬ 
ponding direction, though with various fluctuations and digressions? 
The facts with regard to Fagacere, mentioned by Groom and 
discussed by Thompson (5) certainly complicate the question, but 
the preliminary observations of Tabor, mentioned by Groom, seem 
rather to support the conclusions of Thompson (5) that there has, 
in several cases, been a splitting up of the broad rays into narrower 
ones. 
Professor Groom shows an interesting general correlation 
between increase of the distinctness of the spring zone of large vessels 
and the replacement of narrow rays by broad ones. Both these 
phenomena are also apparently correlated, in a general way, with 
change from the evergreen to the deciduous habit. 
The whole subject requires further investigation, and (we may 
add) fuller detailed description and illustration before we can arrive 
at a safe judgment on the theories put forward, but a fair primd 
facie case may be said to have been established. 
Some of the terminological suggestions of the American authors 
are not very happy. It is true no doubt that it is a mistake to call 
the broad rays of the oak primary, but it would scarcely be advisable 
to transfer the term to the narrow rays because they are thought 
to be primitive. It is much better to restrict the term primary to 
rays composed of primary tissue alone. This was pointed out many 
years ago by Scott, who tried to substitute the term principal for 
the broad rays separating the wedge-like masses of secondary xylem 
in various plants. Where the phylogenetic sequence of ray forms 
is well established the term primitive might be applied to a 
certain type of ray (e.g., the uniseriate ones), but the term 
uniseriate has the merit of being accurately descriptive without 
implications. The term multiseriate., however, cannot reasonably 
be restricted to the narrower multiseriate rays merely because it is 
desired to separate them from the broad multiseriate rays, owing 
to a supposed difference of origin. The terms “broad” and “narrow” 
may be kept for the present: the word compound seems better 
applied to an aggregate of small rays which have not yet formed a 
completely homogeneous structure. A. G. T. 
