Notes on Recent Literature. 
3 6 5 
phylogenetic conclusions, to realise how little such methods were 
adopted forty, or even thirty, years ago. The phylogenetic stand¬ 
point is conspicuously absent from the writings of most of the 
workers of De Bary’s generation, and in the writings of Sanio (so 
far as the reviewer is aware) there is no expression of any such 
phylogenetic theory as the one indicated. Nor is there anything in 
Sachs’ “Lehrbuch” (alluded to by Bailey) which implies anything 
of the kind. Sachs describes the primary structure and secondary 
thickening in the hypocotyl of Ricinus communis quite correctly in 
the main ; the mistake he made was in taking it as typical of the 
structure of the dicotyledonous stem (epicotyl). No doubt many 
text-books have repeated Sachs’ mistake and stated the facts of 
structure in a misleading and even an inaccurate way, hut there has 
scarcely been in existence a deliberate phylogenetic theory which 
derived arboreal from herbaceous plants in the way indicated. 
Thompson (5) has extended the researches of Eames and 
Bailey to Casuarina, the Ericaceae, and the Proteaceae, and concludes 
that in these woody plants, as well as in various Betulaceae and 
Fagaceae, the broad “ compound ” ray has, during descent, been 
broken up to form what he calls “ multiseriate rays,” two or more 
cells wide (sometimes also uniseriate rays) which have “ spread 
through the wood in the higher dicotyledonous Angiosperms.” 
“ Reversion ” to the broad “ compound ” form is found in the seed¬ 
lings of some of these forms. The broad compound ray is often 
found in association with the leaf-trace, and breaks up into several 
“multiseriate” rays as it is traced outwards and upwards through the 
secondary wood. In other cases no broad rays are found at all. 
This interesting work is being continued in Professor Jeffrey’s 
laboratory in various directions and certainly shows that the 
comparative study of secondary tissues is likely to give results of 
phylogenetic significance. But considerable caution is needed 
in accepting far-reaching conclusions based on rather narrow 
foundations. When we are told that the broad rays of the oak- 
type are on the one hand compounded of primitive uniseriate 
rays, and on the other hand may break up into multiseriate (narrow) 
and apparently also into uniseriate rays, it is obvious that the 
greatest care is required in interpreting the results of observations. 
Particularly the tendency to interpret the changes which occur in 
the progressive formation of a given ray or group of rays at a given 
point in the stem in terms of phylogenetic change in the rays of a 
genus or group of species needs very careful checking. This ten¬ 
dency is rather conspicuously apparent in Thompson’s paper (5). 
It seems a pity that the illustrations of all these papers (as is 
generally the case with the anatomical work of Professor Jeffrey 
and his pupils) should be rigidly confined to photographs of sections. 
In some cases these photographs show clearly what they are 
intended to show. In other cases they do not, and should be re¬ 
placed or supplemented by drawings and diagrams if the structures 
described are to be made completely clear to the reader. 
Professor Groom (6) devotes the second part of his paper to 
a consideration of the evolution of the medullary rays of Quercus 
as a result of the investigation of the secondary wood of a consider¬ 
able number of species. He contemplates the possibility of evolution 
having proceeded in either direction—from broad rays to narrow 
ones by subdivision, or from narrow rays to broad ones by aggre¬ 
gation—or in both, and refuses to decide between the alternatives. 
