The Morphology of Angiosperms. 
205 
Balanophora. In the aquatic genera Lenina and Leninocharts the 
structures within the embryo-sac are greatly reduced, and fertili¬ 
zation has not been observed, though it probably occurs occasionally 
in Lenina. If the theoretical value of the triple nuclear fusion is 
to be discounted because in a few cases endosperm tissue can be 
formed without it, we ought to think less of the importance of the 
fusion of male and female elements in ordinary embryo-formation 
because a few instances of parthenogenesis have recently been 
well authenticated. 
The chapter on the Embryo (IX., p. 187) is particularly valuable 
as so much has recently been published on the subject, and it is all 
included in this admirable account Not less welcome is the very 
full bibliography. Here too, as in the preceding chapters, the 
illustrations are for the most part drawn from original sources. 
They are very largely reproduced from memoirs published under the 
direction of the authors. 
The subject of classification, depending mainly on floral 
structure, is treated in the three succeeding chapters (X—XII.) 
The authors give a general sketch of Eichler’s scheme as modified 
by Engler, which cannot fail to be valuable to those readers who 
have not studied systematic botany at first hand. One assumption, 
first expressed in an earlier chapter (p. 10), but underlying the whole 
argument in this section, will strike many botanists as somewhat 
sweeping. “The vast majority of simpler flowers are better 
regarded as primitive than as reduced forms.” The authors add: 
“ At present this is at least a valuable working hypothesis, for it 
coincides in general with the morphological and historical evidence 
concerning relationships as well as with the doctrine of evolution.” 
The doctrine of evolution undoubtedly reveals a general ten¬ 
dency to increasing complexity of structure brought about by 
increasing competition between organized forms. The competition 
among herbs for light, perhaps, first produced plants taller and more 
spreading than their neighbours, and in the end trees came into exis¬ 
tence with all thedifferentiation of vegetative structure necessary to 
secure mechanical stability, a sufficient water supply, and so on. 
But this general advance is modified at every stage by two factors 
which make for simplicity. In the first place it may well happen that 
some structure which at first gave its happy possessor an advantage 
over his fellows is in the end beaten in the struggle for existence by a 
similar structure of improved pattern which performs the same 
functionwith less expenditure of material. This may be the reason 
