478 BOTANICAL GAZETTE 



[JUNE 



The second alternative is the basis for the proposed ontogenetic theory of 

 alternation, the assumption being that the two germ cells of a life-history, although 

 one is haploid and the other diploid, have potentially the same morphogenedc 

 properties, and under the same conditions would produce similar structures 

 In the case of the very dissimilar generations of bryophytes and pteridophytes, 

 the causal differences in the conditions of development are expressed broadly as 

 follows: the spore develops free, in direct relation to soil, water, light, etc.; the 

 lertihzed egg develops in relation to the body of the sexual generation. The egg 

 is thus removed from all the influences acting on the spore, and is exposed to a new 

 set of nutritive and "correlative" influences proceeding from the parent body. 



determined 



determined 



lively short association of egg and gametophyte among pteridophytes, as by their 

 much longer association among bryophytes. 



It is evident that this theory regards the two generations of each species as 

 homologous, ,n that they are developed from germ cells with the same morphoge- 

 netic powers. The really important comparisons to make, therefore, are between 

 gametophyte and sporophyte of the same plant; rather than between the sporo- 

 ph> e of ferns and gametophyte of liverworts, for example. The author promises 

 a lull discussion of the application of this theory in future papers, but in the present 

 one he gives a very brief outline of its application to ferns, lycopods, and horse- 

 tai s, comparing the two generations in each group in a most suggestive wav. 

 the chief value of a theory lies in the work it stimulates, this ontogenetic theory 

 snould^prove of great value, for it opens a large vista of experimental work.- 



Morphology of Ruppia. -Graves" has investigated Ruppia maritima in 

 a its aspects, presenting under the title of morphology, not only the gross and 

 mmute teatures of its morphology, but also its anatomy, ecology, and physiology, 

 such a compendium of statements in reference to a single species is unusual, 

 or m general an investigator in these days is compelled to restrict his attention 

 to one aspect of plants. For this reason, it is impossible for the reviewer to recog- 

 nize the contributions to knowledge that must be imbedded in the general account, 

 except in a somewhat restricted division of morphology. The general outline 

 ot topics is as follows: Morphology of the vegetative organs (46 pp.), in which 

 ne structure and function of stem, leaf, and root are described in great detail 

 and contrasted with those of n th» r tw„-„„^ «... * ., f .„_.*. ♦:,.„ 



organs 



Ecology 



P " ( * «*■'' '" wmcn tne hydrophytic and halophytic adaptations are pre 



^ men, and the difficult problem of adaptation and heredity discussed; Repro 



uc ne organs (18 pp.), i n which flower, sporangia, gametophvtes, fertilization 



and endosperm are described; Embryo; Fruit and seed; Seedling. ~- ~ 



CU)ae>WlthtV SUI ™aries and a bibliography of 98 titles. 



Sr; " GRAVES ' A ' H > The morphology of Ruppia maritima. Trans. Conn. Acad, 

 be. 14:59-170. Ph. i-i 5 . Ji gs . J3 . Ioo8 . 



The paper 



