286 



THE GARDENER'S MONTHLY 



[September, 



that which shows. The standard reference book, 

 " Treasury of Botany," is indebted for a good 

 part of it to his pen, as also is the Botany and 

 Horticulture of the Encyclopasdid Briltanica. Mr. 

 Moore still continues lo edit the Florist and Po- 

 mologist, and in many ways less imperative 

 thou>!;h no less useful, his pen will continue its 

 valuable work. 



On his retirement from the Chronicle his 

 many admirers presented him with a silver 

 pitcher and a purse of $1,500. 



The Penn Monthly.— The publication of this 

 interesting magazine ceased with the issue of 

 the July number. 



How TO Overcome the Potato Disease.— By 

 J. L. Jensen, Director of Bureau Ceres, Copen- 

 hagen, Denmark. Translated from the Danish 

 to English, and published by John Menzies & 

 Co., Glasgow, Scotland. This is a treatise of 

 sixty-tlve pages, and one which deserves more 

 than usual consideration. It is written by a 

 gentleman of high scientific attainments, and of 

 vast practical experience, and a careful reading 

 of his work brings the conviction that he is on 

 the right track. 



The potato disease is well known to be caused 

 by a fungus, Perenospora infestans. It does not 

 follow diseased or sickly vegetation, but feeds on 

 the healthiest as well as the weakest. It is the 

 only cause of the disease. This is well known 

 to be beyond- question. There are, of course, 

 climatic reasons which will favor more vigorous 

 growth and more vigorous destruction some sea- 

 sons than others, just as there are some seasons 

 when grass or grain grow better one year than 

 another. Another fact is that some varieties 

 seem to suffer more than others — that is to say 

 while a plant of one kind, with the disease, has 

 many bad tubers, another kind, with the disease, 

 has the tubers comparatively s'ound. As the 

 disease attacks all alike, and as the constitution 

 of the potato in all varieties is alike, Mr. Jensen 

 was led to examine the cause of this. He found 

 that those varieties which rooted deepest — that 

 is those which buried their tubers the best, were 

 most free from disease. This he thinks reasona- 

 ble from other considerations. The spores of 

 the fungus are conveyed through the atmosphere 

 to the plants. Earth is a protection. The spores 

 can only get to the tubers by being carried by 

 rains through the earth, or by dew down the 

 main stem ; the forther from the main stem and 

 the deeper the tubers, the greater the protection. 



On this reasoning many experiments were made, 

 which are detailed in his work, proving that the 

 deeper the potatoes the greater the protection. 



So he earths up the potato. He finds no 

 difference in the quantity per acre between flat 

 culture and earthing up; but he does find a re- 

 markable freedom from disease by earthing up 

 just as much as the potato plant will bear. The 

 ordinary method of earthing up ridges does not 

 do this well. The earth is made dee[)er about 

 the stems where there are no potatoes, but it is 

 left thin just where the potatoes are. This is the 

 pith of the volume, one which it will profit every 

 large potato grower to peruse. 



Contributions to American Botany. — By Asa 

 Gray. Professor Asa Gray, though he must have 

 no very distant views of a "threescore and ten," 

 still continues to work as hard as ever, for which 

 the great world he lives but to benefit by his 

 knowledge, will be very grateful. This essay, 

 contribued to the American Academy of Arts 

 and Sciences, is one of great value. It is enti- 

 tled studies of Aster and Solidago in the older 

 Herbaria. The "year in Europe" which so many 

 take for relaxation, was chiefly spent by Dr 

 Gray in examining material for the continuation 

 of his synopsis of the Flora of North America. 

 In the course of his studies he found very much 

 which threw light on these two very difficult 

 North American Genera, and this information 

 is the chief topic in this " contribution." Then 

 there are descriptions of new plants of Arizona 

 and adjacent districts, of interest to horticultu- 

 rists ; may be a new horse chestnut, ^sculus 

 Parryi, allied to A. Californicus ; a new black- 

 berry, between Rubus pedatus and R. chamse- 

 niorus, called R. lasiococcus, although these 

 species have not, so far, entered in any way into 

 garden culture ; a new Ribes of the black cur- 

 rant section, R. viburnifolia; several new Pent- 

 stemons and a large number of composite plants. 

 There are eighty-eight new species in all. When 

 we remember that it takes an immense amount 

 of research before we can be sure an unknown 

 plant is new, we may have some idea of the 

 great labors of Dr, Gray on this large number. 



The number also shows that this great country 

 has by no means been all explored when such a 

 great number of novelties can be found in two 

 or three years of botanical rambles. Many en- 

 gaged in this work have not been forgotten by 

 Dr. Gray, and we find among the new plant 

 names, some in honor of such well known col- 



