10 Wisconsin Academy of Sciences, Arts, and Letters. 
the diploid number is sixty-four. Since this is considerably 
less than the lowest number found in the abnormal variety, 
the authors conclude that the latter has at least the diploid num¬ 
ber. The variability of the number at different points in the 
life history is held to be real and not due to errors in counting. 
5. Lastraea pseudo-mas var. polydactyla. The sporophyte 
produces spores and the prothallia grown from them have sixty- 
five chromosomes. The prothallia do not bear archegones. 
Vegetative nuclei from adjacent prothallial cells come together 
and fuse to form the beginning of the new sporophyte. Several 
fusion figures are shown. The sporophyte grown from these 
diploid cells contains one-hundred and thirty chromosomes. 
6. Lastraea pseudo-mas. var. cristata apospora. Here, too, 
there is apospory and apogamy. The prothallium grows from 
marginal or superficial cells of the frond. It bears antheridial 
sacs but no archegones. The sporophyte forms vegetatively on 
the prothallium. The counts of chromosomes which vary be¬ 
tween sixty and seventy-eight at different points in the two 
generations show in the author’s opinion that it is the reduced 
chromosome number that is present throughout the life history. 
Vathansohn (72) concludes that exposure to higher tem¬ 
peratures for a limited time stimulates the development of 
apogamous embryos from the gametophytes of Marsilia Drum- 
mondi. 
Shaw (82) calculated the percentage of embryos formed from 
isolated macrospores of Marsilia Drummondi and compared 
this with the percentage formed when macrospores and micro¬ 
spores remained together. The percentage of embryos formed 
in the first case is considerably lower than in the last. 
Strasburger (88) in 1907 made a cytological study of Mar¬ 
silia Drummondi and related species. In the macrosporange 
Strasburger finds fewer than sixteen spore mother cells. One 
instance is mentioned where there were only four. This is in 
marked contrast with the conditions in such species as M. 
vestita, M. elata and M. hirsuta in which the invariable num¬ 
ber is sixteen. These spore mother cells pass into a synaptic 
condition perfectly normal in appearance. Subsequent to 
synapsis, Strasburger observes a lack of uniformity in the ap¬ 
pearance of the spore mother cells. Some nuclei are larger and 
