232 Notes and Gleatiings. 



The Verbena Disease. — In the March number, your correspondent, Mr. 

 A. Veitcb, seems to be in doubt as to the cause of this disease, and asks for 

 information on the subject. Long experience in the cultivation of the verbena 

 has given me ample opportunity for observation, which has led me to the conclu- 

 sion that the predisposing cause of the disease is debility in the plant ; which 

 condition invites the attack of a microscopical insect, producing the black and 

 crisped appearance which we call "black rust." 



Of the presence of this insect any one can satisfy himself by subjecting a 

 portion of an afTected leaf to a microscope having a power of three or four 

 hundred diameter : the insect will be plainly seen, having the appearance some- 

 what, and the motions, of some varieties of water insects. 



I have said the predisposing cause is debility, or lessened vitality of the plant : 

 this debility may be caused by uncongenial or exhausted soil, or by violent 

 change of temperature or moisture ; in short, any thing that will check growth, 

 and impair the vigor of the plant. In my recent work, " Practical Floriculture," 

 in alluding to this subject, I mention an instance that came under my observa- 

 tion last fall, which of itself proved most conclusively that a lessened vitality of 

 the plant invites the attack of this insect, which produces the effect we call 

 "black rust." In September of last year, I had a lot of about five hundred 

 heliotropes in fine healthy condition, growing in two-inch pots. Requiring a por- 

 tion of them to be grown larger, about one-half of them were shifted into three- 

 inch pots : these were kept side by side with the unshifted half, and treated in 

 all respects the same. Those shifted grew vigorously and strongly, while the 

 unshifted remained comparatively stunted ; and, in two months after, they began 

 to show unmistakable evidence that the insect was at work ; and an examination 

 by the microscope revealed them on every plant : while, on those that had been 

 shifted, not a sign of rust, nor an insect, could be found. 



For a similar reason, we find, that, when we plant out our verbena-plants in 

 May, by August they get exhausted in producing flowers and seeds, the vigor 

 of the plant is lessened, and the condition inviting the insect is again present. 

 Our practice, then, to remedy this, is to crop off all tlie flowering-shoots, fork 

 up the soil lightly in and around the plant, and top-dress with a rich compost 

 (rotted manure and loam in equal parts) to the depth of two or three inches : in 

 this new roots are quickly formed, developing a healthy growth, which gives us 

 the necessary soft and healthy shoot that we use for propagation in September. 



This is our summer treatment : that for fall and winter entails the same con- 

 ditions. The cuttings first are taken soft and succulent, never allowed to wilt, 

 potted at once when rooted, and cared for throughout, so that the root is never 

 allowed to get hard by dryings or the sap checked by any sudden change of tem- 

 perature. To avoid this, to the best of our ability we keep as near an average 

 temperature of 40° at night as possible ; giving ventilation at all times when 

 practicable. In addition to this, all our verbena-houses are fumigated by tobacco 

 at least twice each week. Although tobacco-smoke, I know, will not directly 

 destroy the verbena-mite, yet I am of the opinion, that, if you start with a healthy 

 stock, it will never exist to injure if fumigation is persisted in twice a week. 

 Such is my own experience, where for the last fifteen years I have grown from 



