It was an agreeable surprise to find my inquiry concerning the application of linseed oil upon pear trees in the Gardeners' Monthly of October turn out so encouragingly, and undoubtedly many of your readers will thank you for this repetition of your experience, and which being so well and clearly stated, none need go astray who may choose to experiment in the matter. But touching upon the Bacterian question, you apparently put a wet blanket on the whole theory; and I am in much doubt whether you will think enough of my present good intentions should I offer a resume, in as compact a form as possible, of this extremely interesting question, so that any of your readers who may not have been hitherto attracted by its allurements, or favored with opportunities of research in Bacterial movements, may now be led to investigate for themselves concerning these smallest of all organisms, as affecting the destruction and premature death of their pear trees.

So far as the pro or con in this case is concerned, I will first bring the opponent of the Bacterian theory mentioned by you before your readers in the person of Professor Penhallow, of Montreal, and place a supporter of the theory in the person of T. J. Burrill, of Illinois, face to face, and thus leave these gentlemen before an intelligent audience to adjust their differences, whatever they may be, in this praiseworthy research. Meanwhile I will go on with my proposed chat, hoping thereby to enlist some of your readers as microscopical investigators, and as reporters of any fruitful results they may have to offer.

As a beginning on this question I will say that in grouping these researches from a multitude of authorities they reach into the hitherto mysterious, but now rebound into the light of day, and bright enough no doubt hereafter to interest and attract those who are desirous of unfathoming the deep secrecies of nature, and some tangible remedy will in time probably be forthcoming to ward off these invaders of both vegetable and animal nature.

Bacteria are known "as the most widely diffused of all beings." They are not a spontaneous generation as some have put forth; but one has aptly' asserted that, like animals and plants, however they may have once originated, are only propagated now by the law of continuous succession, and in support of this another has said that life has never been found to arise independently of pre-existing life, and claims life as derivative of life; and in recent " Philosophical Transactions" it is arerred that it would be monstrous to affirm that the swarming crops of Bacteria are of spontaneous origin. Bacteria form the boundary line of life; beyond them life does not exist. The strongest magnifying power adapted to this investigation yet attained, to search into the depths of this all-absorbing subject, is the immersion system of Hart-nack and possessing a magnifying power of 3000 or 4000 diameters. Nearly all Bacteria have two modes of life - one of motion - the other rest. When they swarm in water, moving amongst each other, they are said to present a spectacle similar to a swarm of gnats or the busy ant hill when in commotion, and apparently dodging each other and moving in all directions.

With respect to what the motion of Bacteria depended upon recent researches point to the fact that cilia is to be found in all true Bacteria; Ehrenberg being the first to maintain that the motion of Bacteria depended upon vibratile cili. Whether Bacteria has a vegetable or animal nature Sacks is said to solve the question by uniting the algae and fungi in a single group, the thallophytes, and establishing a series exactly parallel. Bacteria swarm only where there is favorable temperature, plenty of nourishment, and the presence of oxygen, and their power of multiplication is said only to be limited by the absence of nutrition. Their propagation depends upon bi-partition ("fission") at maturity and constricts itself in the center, resembling the figure 8 and breaks into two new individuals; each of these again in a short time dividing into two others, and each of these again dividing, either constricted in the middle or hanging in pairs. The warmer the air the quicker the division proceeds and the stronger the multiplication, and in such incredible masses that the following computation may be looked upon with amazement, viz.: that from a single Bacteria in twenty-four hours will increase to sixteen and a hal: millions, and so on in proportion to numbers.

No wonder, then, that your pear trees sink rapidly from this foreign besieger of health anc longevity'settling (presumedly) upon them. Friscl says reproduction is made only under the influence of free air. They never fail in air or water, and attach themselves to all firm bodies, but develop themselves only where fermentation, corruption, etc, are present, and multiplying in moist air wherever they can find decaying matter. Putrefaction, decay, etc., are chemical changes excited by Bacteria, and all circumstances which hinder this development delay their destructive effects. Bacteria live upon the fluid soil upon which they invade, and it is highly probable that they are the conveyors and originators of the ferment contagion. Extremely low temperature does not destroy them but simply numbs them.

It will be seen, then, from this outline of the subject before us, that the vital point for our consideration is to prevent the prodigious multiplication of Bacteria, and which, so far as vegetable physiology in this case is concerned. If permitted to do so, I will give a future paper, and partly by the aid of this synopsis, suggest possible remedies for the evil. The microscope is one great assistant in the study of this absorbing topic, and I hope the readers of the Monthly will be sufficiently interested in this wonderful domain of study to awaken them to action, 50 Gregory St., Rochester, N. V. [It was not the editorial intention to discredit or endorse the Bacterial theory of pear blight. We do not know that linseed oil will protect a pear from the disease, as we have been supposed to say. We think it highly probable that it would; but we have no actual evidence that would satisfy science, and we desire to maintain a distinction between that which may be and that which is.

It does not weaken Prof. Burrill's position that Prof. Penhallow believes him wrong in his conception of the cause of the yellows; nor is Prof. Pen-hallow's position less likely to be true because Prof. Burrill has other conclusions; but that which is merely likely to be true, and which requires labored arguments in demonstration, is not science, and should have no place in purely scientific papers. We wished to emphasize this point, and not to offer any opinion, one way or the other, on the very valuable suggestions of both professors. - Ed. G. M].