No. 401.] REVIEWS OF RECENT LITERATURE. 449 
cetes which at all resembles the free cell formation in the ascus, 
where the spores are cut out of the ascus plasm by the revolution 
of the aster rays. In the Phycomycetes we have isolation of the 
*protospores" by successive irregular segmentations, not simulta- 
neous, but progressive. ‘This progressive segmentation has no 
parallel in the asci, where from the start a single nucleus forms the 
center for the formation of each daughter-cell”’ (p. 517). Harper 
finds it possible to connect the cleavage processes of the Phycomy- 
cetes with other cases of division by constriction, as in cell division 
in Cladophora, or in the abstriction of conidia in Erysiphe, as 
described by him, but he finds no connecting link between this 
general process of spore delimitation and free cell formation in the 
ascus. This stands as opposed to the older view of Brefeld that 
the ascus merely represents an evolution out of the ancestral sporan- 
gium, from an indefinite to a definite number of spores of definite 
size and form. Moreover, in the origin and character of the “ epi- 
plasm," regarded as a distinctive feature of the ascus, and that of 
the * episporal slime " of the sporangium, Harper finds no connection 
whatever. A possible origin of the processes seen in the ascus is 
suggested tentatively in such phenomena as Strasburger described 
(Zellbildung und Zelltheilung) for swarm-spore formation in CEdogo- 
nium. This, however, the author has not as yet been able to confirm 
by personal investigation. 
The general conclusion is that the Ascomycetes cannot have 
arisen from the Phycomycetes, — the ascus seems to stand by itself 
as a peculiar structure, whose origin is at present in obscurity, — and, 
finally, the author's researches, together with those of Thaxter on 
the Laboulbeniacez, seem to point very strongly to a multiple algal 
origin of the fungi and the subsequent independent evolution of 
certain forms of spore production by different groups. 
H. F. ROBERTS. 
Notes. — The Cactaceæ of the Galapagos Islands are passed in 
review, by Dr. Albert Weber, in the Buletin of the Paris Museum 
for 1899, and four species are recognized, of which two, pertaining 
to the genus Cereus, are characterized as new, while the other two, 
belonging to the genus Opuntia, were described and named in 1898. 
. Purpus, of the Darmstadt Botanical Garden, publishes an 
article on North American cacti which have proved hardy in Germany, 
in Die Gartenwelt of January 7. Several reproductions from photo- 
graphs represent the species referred to. 
