166 General Notes. [February, 
THE PRopucTION OF MALE AND FEMALE P ants. — Recent 
observations and experiments by Hoffman (Bot. Zeit., 1885) con-* 
firm the view hitherto held by some biologists that the produc- 
tion of the male organism is due to insufficient nutrition. In 
Lychnis diurna and vespertina, Valeriana dioica, Mercurialis annua, 
Rumex acetosella, Spinacia oleracea and Cannabis sativa dense 
sowing increased the amount of male plants. 
Pear BLIGHT BACTERIA AND THE HorTICULTuRISTS.—AlIthough 
to the mind trained in the logic of investigation there can be no 
doubt as to the cause of pear blight, there are yet some horticul- 
turists who do not feel convinced. With them the facts—plain 
facts—brought out by Mr. Arthur at Ann Arbor, and reproduced 
in popular form in the December NATURALIST, are spoken of as 
the “ Bacterian theory of pear blight,” when as a matter of fact 
there was no “theory” in the presentation. As was remarked 
by one of the auditors at Ann Arbor, Mr. Arthur’s paper 
amounted to a demonstration, and as a demonstration it must be 
accepted. One may as well attempt to controvert a demonstra- 
tion in geometry as to attempt it in this case. 
We have observed two principal varieties of denials, and both 
illustrate the fact that the mind untrained in the methods of scien- 
tific reasoning is most incredulous of demonstrations, and most 
credulous of unproved assertions. (1) It is held on the one hand 
that the bacteria observed are an accompaniment and not the cause 
of the disease, and this in face of the fact that all of Mr. Arthur's 
investigations were directed to this very point, Professor Burrill 
having long ago shown the presence of bacteria beyond a doubt. 
Our horticultural friends must bear in mind that Mr. Arthur's 
work was not to find whether bacteria ave present in pear blight. 
Of that almost any one who has access to a microscope can sat- 
isfy himself with but little labor. He undertook the solution of 
the very matter which is now brought up so calmly, innocently 
and confidently. And he made no announcement until the dem- 
onstration was reached. Let our friends read the testimony can- 
didly and they will be fully satisfied upon this point. 
(2) It is held by another class of disbelievers that what Pro- 
fessor Burrill and Mr. Arthur have been working upon is a kin 
‘of blight which is quite distinct from the real Simon-Pure blight 
which works such havoc in the orchards. That is, we have here 
an attempt to diagnose off-hand, out of sight and hundreds of 
miles away, the disease to which two trained men gave years of 
close personal study. 
But science is patient, and no doubt the next work of Mr. 
Arthur will be the study of cases of this so-called other kind of 
blight. It will then be interesting to know what new line 
defense will be set up by those who “do not believe in the bac- 
terian theory of blight.” i 
BotanicaL News. — Late numbers of the Botanische Zeitung 
contain articles as follows: The pith rays of the Coniferæ, by A- 
