216 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
The following new North American genera are described by Mr. A. 
P. Morgan : * — 
Lentodium (Agaricini). Pileus fleshy-coriaceous, tough, hard when 
dry, persistent ; stipe more or less elongated, tough, central or eccentric, 
confluent with the hymenophore ; hymenium porose-cellulose, the lower 
surface veiled by a thick persistent membrane, which is at length radi- 
atcly dehiscent ; spores white. 
Argynna (Ascomycetes). Peritheces superficial, carbonaceous, sub- 
globose, naked, astomous, breaking up irregularly ; sporids fuliginous, 
uniseptate, papilionaceous. 
Pyrenomyxa (Ascomycetes). Stroma superficial, pulvinate. the sub- 
stance black and carbonaceous, composed mostly of large confluent cells 
w r ith thin, fragile walls, their large mouths covered by a uniform 
continuous layer; sporids navicular, brown, continuous, produced in 
spherical or oval clusters of eight, lying edge to edge. 
Under the name Trichoseptoria Alpei g. et sp. n., Dr. F. Cavara f 
describes a parasitic fungus which causes black spots on the fruit of the 
lemon. The following is the diagnosis of the genus, belonging to the 
Ascomycetes : — Perithecia carpophila, innato-erumpentia, maculicola, 
trichomatibus undique fulta, membranacca ; basidia nulla; sporulae 
bacillares, septatae, hyalinoe. 
Karyology of Saprolegnia. f — Mr. A. H. Trow has studied the 
structure of the nucleus and its mode of division, as well as the pheno- 
menon of conjugation of nuclei, in several species of Saprolegnia and 
Adilya. The following is a summary of the results at which he has 
arrived. 
The nucleus in the genus Saprolegnia is bounded by a nuclear wall, 
and possesses one central chromosome of spongy texture. The space 
between the nuclear wall and chromosome is occupied by a nucleo- 
hyaloplasm, which is traversed by fine threads. The nucleus undergoes 
direct division in the zoospore and mycele, and the products of these 
divisions ultimately pass into the sporanges and gametanges. In the 
oogones and antherids each nucleus undergoes one reducing division by 
an indirect method, in virtue of which the whole chromosome becomes a 
half-chromosome, but no fusions of functional nuclei take place. The 
number of gameto-nuclei produced in the oogone by the reducing 
division is about twenty times greater than that necessary to provide 
one nucleus for each oosphere. The number is reduced by the degene- 
ration of the excess. Most of the gameto-nuclei in the antherids and 
fertilisation-tubes also undergo degeneration. 
Fertilisation takes place invariably in S. dioica , and at least occasion- 
ally in S. mixta, Adilya americana , and another species of Adilya; while 
S. Thureti is normally apogamous. The whole chromosome condition 
is restored to the nucleus either by the sexual process, or by a process 
of growth. The two gameto-nuclei do not fuse to form the single zygote- 
nucleus until a late stage in the maturation of the oospore. The Sapro- 
legnieae as a group arc not apogamous. At the period of germination 
* Journ. Cincinnati Soc. Nat. Hist., xviii. (1895) pp. 36-15. 
t Atti 1st. Dot. Pavia, iii. (1891) pp. 37-44 (1 pi.). 
% Ann. Bot., ix. (1 895) pp. 609-52 (2 pis.). 
