1896] CURRENT LITERATURE 425 
vegetation is touched upon in a bulletin by L. A. Clinton (Cornell Bull. 120), 
and in one by F. W. Rane (N.H. Bull. 34), the latter treating of irrigation. 
—J.C. A. 
THE BOTANICAL SEMINAR of the University of Nebraska has published, 
asaspecial brochure, an address recently delivered under its auspices by 
Professor Conway MacMillan, entitled ‘Some considerations on the alterna- 
tion of generations in plants.” The discussion is interesting and suggestive, 
and the “ main contention” is summarized by the author as follows : 
“The definition of rudimentary alternation should be widened so as to include 
rejuvenescence of the syngamete.” 
By “rudimentary alternation” is meant that form of it in which the indi- 
rect development of the sexually formed cell (syngamete) does not result in a 
distinctly organized body. In this category the author would include not 
_ merely the cases in which the syngamete produces directly several zoospores, 
as in Spheroplea, but also those in which there is merely rejuvenescence, as 
in the zygospore of Spirogyra. 
“Indirect development of a cell resulting from a sexual process is most funda- 
mentally a sensitization and serves to compensate for that general sexual immobility 
which arises from the preponderant constructive chemism of plants.” 
Alternation of generation is generally spoken of as a device by which the 
product of the sexually formed cell is multiplied, and hence the more highly 
developed the sporophyte the greater the advantage. Our author, however, 
sees in it something deeper, which he calls “sensitization,” by which he 
means the bringing of a syngamete cell “into more intimate reciprocal 
relations with the environment,” as seen ina primitive way in rejuvenescence. 
is, he thinks, is an offset to the general stability of plants, a stability which 
follows: from their essentially constructive character, as opposed to the 
destructive character of animals, 
nomena in 
h and is the 
. 
ea sora is as distinctly a structural response to the plant t f che ca 
: i$ a structural response to the animal type of chemism. Sporophytization, there- 
ore, In the € wi é 
tion j plant phylum, is a phenomenon of coordinate importance wit! p nae 
vn the animal, and homologies between the vegetative tracts of the higher pian 
higher animals lie below the plane of the cell unit.” 
ity € author also presents a “classification of alternation of gene 
i ‘ 
ch may be of interest to some as a new setting for old facts. 
rations,” 
A. Recapitular alternation. 
B. Heteroblastic development. 
C. Sprout alternation. 
Lb. Homologous alternation. 
Alteration 
types. 
