386 BOTANICAL GAZETTE [May 
the author’s point is that the real distinction lies in the rejuvenation of the 
cell or cells in the case of germs and the absence of any such change in the 
case of buds. “Spores and seeds,” he says, ‘‘are germs in the sense that in 
their production rejuvenation of a cell has taken place; that the former have 
arisen in a purely asexual manner and the latter have arisen by fertilization 
is a secondary difference which is without significance for multiplication. 
In contrast to this “in multiplication by buds no rejuvenation occurs, but only 
a growth by ordinary cell division.” 
In the second chapter Mébius undertakes to show that the idea that plants 
continuously propagated by cuttings, offsets, tubers, etc., become weakened 
and are more liable to epidemic diseases, has no basis in fact. In combating 
this idea he brings together many interesting facts regarding both wild and 
cultivated plants which are propagated vegetatively. 
The third chapter, “on the conditions upon which the blooming of plants 
depends,” is a presentation of the relations of the age of the whole organism 
or of certain shoots, light, temperature, moisture, etc., to blooming. The 
fourth chapter discusses the relation between germ and bud reproduction for 
the purpose of showing that in most cases vegetative reproduction is not the 
primary method but one into which plants have been forced when external 
conditions have repeatedly prevented the formation of flowers or fruit. 
In the last chapter the author shows the steps in the evolution of sexuality 
among the algz, and finds the significance of sexuality in the opportunity it 
gives through crossing for the origination of new species and for the produc- 
tion of more complex forms; z. ¢., to put it as usual, sexual reproduction is a 
prolific source of variation. 
The thesis of the book to which other ideas are subsidiary is that the dis- 
tinction between the modes of reproduction is to be found in the rejuvenation 
of the reproductive cell in one case and its absence in another. This seems 
a very tenuous thread on which to string so many important phenomena. 
That rejuvenation does occur in many cases is readily seen; that it occurs in 
the spores of fungi has been proved in only a few cases, and that doubtfully; 
the rest is assumption. Moreover, since all such distinctions are merely 
y conveniences in the arrangement of observed facts, it strikes us 
that ‘hase is little value in making the thread so fine as to be grasped with 
difficulty when we wish to em a new pearl 8 el strand. upon 2S “ 
gametes is an easily observed will serve pedagog! ical pur-— 
__ poses much better than the new proposition. Thus we may clearly emer 
ee me ‘non-sexual nissan in the thallophytes, among which it is, 
ge es seine vende 
while to tree te _ PVs ihe ee 
. That becomes important o: tes and hight ee 
tion 
ace: it is readily done by ear o the t teres non-sexual to reproduction 
pai by a which. eres rise to the alternate phase in the sp eel es oe 
