STUDIES ON THE GENETICS OP FLOWER-COLOURS, ETC. 95 
Wliat makes the breeding of our plant very difficult is the poor germination 
of seeds. Though each pyxis contains a large number of them many do not 
come very often to germination ; frequently I have met with the cases where 
even no one from one pyxis had germinated, so that some experiments 
described in this paper are based on rather few individuals. Many experi¬ 
ments have been earned on to overcome this difficulty. Since, according to 
my view, the poor germination of seeds would be chiefly due to the difficulty 
of water passage through seed-coats, one of my methods was to rub out seeds 
lightly with coarse quartz sand, so as to injure slightly seed-coats and make 
them easily permeable to water ; this treatment has however given no good 
results Avhatever. Then I have tried the method of high pressure adopted by DE 
Vries : l I have used an autoclave-like apparatus specially made for the 
purpose, and obtained the high pressure by the use of an iron receptacle 
containing oxygen under high pressure (150 atmospheres when full) instead of an 
automobile pump, because when the receptacle is connected with the apparatus, 
the high pressure is attainable instantaneously in the latter. Seeds soaked 
in water during one night and placed in it were subjected by this means to 
the pressure of 8 atmospheres or less during 24 hours, and then sown as 
usual. The following method was made use of in some cases : seeds were 
first treated with 60% or less concentrated sulphuric acid during 30 minutes, 
and after repeated washings, they were soaked in water during one night 
and then sown. The two latter methods above described seem to promote 
the germination to a certain degree, but not so much as might be wished for. 
Seeds from different plants, and later those from different flowers of one 
individual were sown separately. Since seeds of Portulaca are very fine, if 
we pour down water to seed-pans from above as usual, seeds might often be 
thrown from one pan to another, thus causing the mixture of seeds from 
different parents. To avoid this possibility, no water has been given from 
above : a number of seed-pans were placed in a rectangular vessel of wood, 
180 cm. long to 90 cm. wide and 10 cm. deep, partly filled with water, so 
that the latter may go up gradually. 
My study on some of the crosses came already to a certain definite end, 
and I like to publish here its results, because they will, as I think, enable 
i Bot. Gaz. Vol. 59, 1915, pp. 192-193. 
