340 BOTANICAL GAZETTE [NOVEMBER 
parts of South Australia. “It grows terrestrially in seasonal swamps during 
the period of winter rainfall. During the dry summer it aestivates, as do the 
other geophytes with which it is associated.”” The stock is buried, and during 
the vegetative season only a small rosette of linear leaves is visible above the 
soil. On approach of the dry season, the leaves dry up and become detached, 
leaving their tough bases and sporangia upon the stock, wholly buried and 
invisible. 
This species seems to be unique among Pteridophytes in its method of spore 
liberation. There is a special mechanism for freeing the spores which depends 
for its action upon saturation with water, not upon dryness (as in other Pterido- 
phytes). Other peculiar features of the species are in the nature of preparation 
for this remarkable method of spore dispersal. In his summary, OsBoRN de- 
scribes the performance as follows: ‘Early in the rainy season, the hardened 
bases of the sporophylls are forced above the surface of the soil in a projectile- 
like mass, carrying with them the sporangia, by the expansion of certain pads 
of mucilage cells formed at the close of the previous vegetative season on the 
extreme bases of the sporophylls and from the superficial cells of the leaf- 
bearing cortex. About the same time the leaves of the new vegetative season 
begin to appear. The imbricate mass of sporophyll bases breaks up upon the 
surface of the soil, and the spores are set free by a tearing away of the sporan- 
gium wall from its attachment to the sporophyll when sodden. This is due to a 
difference between the tension of the inner and outer surfaces of the sporangium 
wall when saturated, and results in an eversion of the wall.” 
TAKAMINE” has investigated the gametophytes of Isoetes japonica and I. 
asiatica, with some interesting results. The female gametophyte of J. paver 
usually has five or six archegonia, but sometimes ten or more. hen fertiliza- 
tion occurs in one of them, the others degenerate; but in rare cases when 
fertilization occurs in two or more archegonia, several embryos are developed 
up to certain stages. Occasionally megaspores and microspores were found 
in the same sporangium. In J. asiatica the 2x chromosome number is twenty- 
two, while in J. japonica it is “forty-three to forty-five.”” Hybrids of the two 
species were produced, an account of which is promised later.—J. M. C. 
Complexmutation.—As the term mutation is now being used by geneticists, 
its application is restricted to “locus changes”? on the chromosomes. At one 
place on one chromosome, mutation takes place, the effect of the change being 
so restricted as to involve only a single factor; other factors, although lying 
very close on the same chromosome, remain unchanged. Save for “ defi- 
ciency,” noted by BriwcEs" (which is evidently of a different category), all 
mutation seems to have been of this very localized type. It is perhaps sur- 
prising that no clear cases of mutations involving simultaneous changes 1n 
%” TAKAMINE, N., Some observations in the life history of Isoetes. Bot. Mag. 
big 35:184-190. figs. g. 1921. 
™ BripcEs, C. B., Deficiency. Genetics 2:445-405. 1917. 
