( 184 ) 
If again we suppose 4,2, and ls to lie in a plane p then in the 
first place we have to deal with all the conics through one of the 
points of intersection P of those three lines resting on the remaining 
five lines, whilst their planes pass through M. 
Now, according to § 4, P is a twelvefold point of the locus of the 
conics through P resting on five given lines; this locus proving to 
be of degree 18, the right line PM is intersected twice by six conics 
of the surface. In this way we find 18 proper conics satisfying the 
given conditions. 
The line connecting the traces of /,, 1; on p determines with 
M a plane on which J, /; furnish two points of the second right line 
of a degenerated conic. This consideration furnishes 6 conics. 
If the line connecting M with the trace Z, is intersected by the 
transversal t of ls, lo, lj, the line of intersection of p with the plane 
(Mt) completes the line ¢ to a degenerated conic answering the 
question. In this way 8 new solutions are found. 
Finally we find 2 more answers by connecting each of the trans- 
versals of lu ls, lol, by a plane with M; each of the traces of 
those planes on p is then the second right line of the degenerated 
conie. 
Thus we arrive at the conclusion, that u v* = 34. 
Botany. — Dr. W. Burcx, presents a paper: „On the irritable 
stigmas of Torenia Fournieri and Mimulus luteus and on 
means to prevent the germination of foreign pollen on the 
stigma.” 
While occupied last year in Batavia with an investigation about 
the question whether or no there exist contrivances on the stigma to 
prevent the germination of foreign pollen, concerning which I presented 
a paper in the Meeting of September 29, 1900, my attention was 
drawn by a biological particularity of the irritable stigmas of Torenia 
Fourniert. This induced me to a nearer research, which I have 
been enabled to continue in this country on another plant with 
irritable stigmas: Mimulus luteus. 
Irritable stigmas have been known for a long time. Already LINNAEUS 
and KOELREUTER mentioned them, and later they have been repeatedly 
discussed, in particular for the various species of Mimulus !). 
1) See on irritable stigmas: DerPixo, Bot. Zeit. 1867. pag. 284. 
BarariN, Bot. Zeit. 1870 pag. 53. 
Cu. DARWIN, Cross- and self-fertilisation. Chapt. 3. Mimulus luteus. 
A. Hanserre, Phytodynamische Untersuchungen in Sitzungsberichte der Königl. 
Böhmischen Gesellschaft der Wissensch. 1889 IL, p. 308. 
Kerner von MARILAUN, Pflanzenleben II. p. 260. 
