DECEMBER 27, 1906| 
NADU LE, 
195 
tions on the plants in their native habitats, is of great 
interest. The ‘‘larval’’ forms habitually passed 
through by certain plants, e.g., by Veronica epacridea, 
Actinostrobus, sps., and other conifers, 
Leguminose, Eucalyptus, sps., Aloineze, and mem- 
bers of other groups, are also discussed; and 
conditions under which sexual reproduction may occur 
in plants that retain their larval aspect are investi- 
gated. That such plants have been described and 
named as distinct from the usual adult forms is 
well known, and this is seen to have been the 
Eucalyptus and in other groups. 
A chapter on the phylogenetic significance of helico- 
morphy sums up the conclusions of the author. Many 
of the forms he regards as adaptations to environ- 
ment, some of which are unstable, while others show 
the influence of heredity and persist under new con- 
ditions, e.g. the formation of phyllodes by Acacias in 
greenhouses. Some appear to become relatively con- 
stant in a short time, e.g. seasonal dimorphism of 
Euphrasia Rostkoviana and E. montana, believed by 
Wettstein to have become fixed as the result of the 
alpine meadows being mowed, and now retained in 
cultivation in a botanic garden. But, while there 
may in some be a strong hereditary tendency to re- 
petition of the cycle, Diels concludes that each helico- 
morphic stage may be the starting-point of a new 
phylogeny.. He emphatically opposes the belief that 
the helicomorphy of the immature plant necessarily 
represents a condition similar to that of the an- 
cestors ; and asserts that the apparently ancestral form 
has in many cases been acquired in response to the 
environments of the young plant. Acacia insolita is 
quoted as an example of a species descended from 
phyllode-bearers that now habitually produces pinnate 
leaves abundantly when mature; and the position is 
briefly stated thus :—‘‘ We saw that Phylloglossum re- 
sembles the young of many species of Lycopodium. 
But Lycopodium does not for that reason follow 
Phylloglossum in phylogeny; Phylloglossum may just 
as well be younger than the greater number of the 
Lycopods.’’ The assumption that the infantile form 
must in all circumstances represent an older stage 
of ancestry than does the adult is frequently in oppo- 
sition to the facts. A brief review of similar pheno- 
mena in the animal world, and a short bibliography, 
conclude the book. It only remains to add that the 
illustrations are excellent, and that a good index 
makes reference easy to the stores of information. 
various 
the 
case in 
THE RADIO-ACTIVE PEDIGREE. 
By Prof. E. Ruther- 
(London: Constable and 
Price 16s. net. 
Radio-active Transformations. 
fOLG eb. S. Pp. 2875 
€o:,, Ltd.,, 1906.) 
HIS work is, in the main, a reproduction of 
Prof. Rutherford’s Silliman lectures, delivered 
at Yale in March, 1905, and represents his latest 
views on the subject. Some treatment of radio- 
activity in general is given, and then a. detailed de- 
velopment of the special subject of the book. This 
treatment differs only from the author’s previous ex- 
NO. 1939, VOL. 75] 
positions in the greater detail in which the subject is 
worked out. Every month seems now to bring to 
light some hitherto unrecognised stage in the trans- 
formation of one of the radio-elements. One 
suppose, however, that this field of discovery cannot 
be of unlimited extent, and that the full detail of 
the transformations must, before long, be made out, 
so far at least as they are accompanied by demon- 
strable radio-activity. 
It has been usually assumed 
atom throws off an @ particle, 
transformed into an atom of a new product. On 
this view, it can be seen, with a little thought, that 
a mineral in radio-active equilibrium ought to owe 
an equal proportion of its activity to each of the 
products of a series, and there is considerable evidence 
that it is often so. Lately, however, two cases have 
presented themselves which seem clearly inconsistent 
with this. One of them, that of actinium, is men- 
tioned by Prof. Rutherford in the present work. It 
seems that actinium, like radium, is found in uranium 
minerals, and in those only. Further, that the 
amount of actinium is probably, as the amount of 
radium is certainly, proportional to the uranium con- 
tent. If so, we cannot but conclude that actinium 
is a member of the uranium series. Now comes the 
difficulty. Actinium certainly does not contribute 
anything like so much to the total activity of pitch- 
blende as radium and uranium each do. 
The second case is to be found in a paper in 
the October Philosophical Magazine. Moore and 
Schlundt have found that uranium X, the immediate 
product of uranium, gives a small a radiation as well 
as the 8 radiation by which it is mainly characterised. 
It is certain, however, that the « radiation of uranium 
is not much diminished by removing all the 
uranium X from it, hence the a radiation of 
uranium X must be comparatively small. Here 
again the principle of equal activity in each successive 
product of a series is violated. This latter case has 
only been brought to light since the publication of 
the present work, and quite a new light has been 
shed on the case of actinium by Dr. Boltwood’s letter 
to Nature describing the formation of radium from 
actinium. This seems to make it certain that 
actinium is in the main line of radio-active descent, 
and to put out of court Rutherford’s plausible sug- 
gestion that it is the head of a collateral family. 
The subject, indeed, progresses so fast that the re- 
viewer of a bool like this almost always has lights 
which were not available to the author at the time 
of going to press. 
The subject of the possible ultimate production of 
lead by the radium series is here discussed in some 
detail. It is doubtful, I think, whether much stress 
should be laid on the almost invariable presence of 
lead in uranium-radium minerals. An interesting 
spectroscopic investigation by Hartley and Ramage 
(Engineering, September 24, 1897) proved that lead 
was present in almost every one of a very large 
collection of iron ores examined by them. We cannot 
suspect a change akin to radio-activity in this case, 
for lead has a much larger atomic weight than iron, 
would 
that each radio-active 
and becomes thereby 
