326 BOTANICAL GAZETTE [OCTOBER 
hybridize. In this connection it is found that tubes penetrate rather deeply into 
agar. The work with several species of lilies shows that the tubes penetrate 
most rapidly in stigmas of the same species, and progressively slower as the 
species becomes more distant. When the tube penetration was slow in these 
crosses, it became continuously slower as the depth of penetration increased, 
and finally ceased short of the embryo sac. The writer thinks that he has 
shown that this behavior is due to shortage of nutrient or stimulative materials 
and not due to toxic materials. His evidence, however, is not at all against 
the gradual formation of antibodies, a suggestion made by Jost. Self-sterility 
and failure to hybridize, so far as it is due to lack of tube penetration, deserves 
a thorough physiological study in the light of our modern knowledge of anti- 
bodies and of several other phases of physiology. The later evidence (per- 
haps not entirely conclusive) that the character of self-sterility mendelizes does 
not subtract in the least from the need of such an exhaustive physiological 
study.—WILLIAM. CROCKER. 
A new type of embryo sac.—The evolution of the sporophyte and the 
gradual reduction of the gametophyte are well known to every botanist. In 
the angiosperms, where the reduction of the gametophyte generation is most 
extreme, intensive research has revealed several types of embryo sac. Doubt- 
less the most common type and the one long believed to be practically the only 
type is the familiar 8-nucleate sac, two of whose nuclei fuse to form the endo- 
sperm nucleus. This sac is formed by one of a row of 4 megaspores. Soon the 
Lilium type, looking like the preceding but formed from 4 megaspores, was 
discovered. Sacs with 16 nuclei, some formed from four megaspores and 
some from a single megaspore, were added to the list. Cypripedium has a 
4-nucleate sac formed from two megaspores. Since the discovery of the 
Cypripedium type, other 4- holy sacs have been found, some formed from 
one megaspore and some from 
new type of embryo sac — been found in Plumbagella, one of the 
Plumbaginaceae.? The development starts as in Lilium, there being 4 
megaspores, not separated by walls, but there are no further nuclear divisions. 
One nucleus becomes the nucleus of the egg, two fuse to form an endosperm 
nucleus, and the remaining nucleus, which is at the antipodal end of the sac, 
disintegrates. At the time of fertilization, there are only two nuclei in the 
he most important feature is that a megaspore functions directly as the 
egg. The fusion of two megaspore nuclei to form an endosperm nucleus 
is also new. Without question, this is the most reduced female gametophyte 
ever described, and in the nature of the case the reduction can go no farther. 
DAHLGREN recognizes that th« reduction is as extreme as in animals, and he 
compares this sac with the egg and three polar bodies. 
DAHLGREN, K. V. Ossian, ee ilgieue von Plumbagella, ein neuer Typus. 
coe fiir Botaalk 14:I-10. figs. 5. 
