November 21, 1888.] 



Garden and Forest. 



459 



From the large mass of statistical details so obtained the gen- 

 eral result was arrived at, that for each variety the period of 

 time between the sowing and the appearance of the first 

 flower-bud was long in proportion to the slowness of germina- 

 tion. In some cases an interval of five or six days was no- 

 ticed between the seedlings of the two categories. The vigor 

 of the plant was uniformly superior in those cases where the 

 germination was rapid, and, moreover, when subjected to 

 analysis, the amount of dry matter as distinguished from water 

 was always greater in the quickly than in the slowly developed 

 plants. 



But the most remarkable results are those relating to the 

 production of double flowers. In all the varieties the propor- 

 tion of double flowers was greater in the case of those that 

 germinated quickly than in the case of the laggards. Ten 

 plants of one variety with violet-brown flowers, grown rapidly, 

 produced all double flowers, while eight plants of the same 

 variety, which had germinated slowly, produced all single 

 flowers. The following figures convey other striking illustra- 

 tion of the facts now mentioned. Of one hundred plants 

 belonging to nine different varieties, the proportion of double 

 flowers, according to the period occupied in germinafion, 

 was as follows : 



Doubles. Singles. 



After rapid germination 82.56 17.44 



After slow germination 27.03 72.97 



It may be suggested that the superiority might be attrib- 

 utable to the varying influence on the same seeds of light, 

 heat or moisture ; but the experimenters reply that the ten- 

 dencies e.xist in the seeds themselves, for the two categories 

 of seedlings were exposed to identically the same conditions, 

 and yet showed the differences already mentioned. More- 

 over, although those seedlings which were grown on in sterile 

 sand were much less vigorous than those grown in good soil, 

 they, nevertheless, showed corresponding inequality as re- 

 gards their flowers. Again, next to never was a single flower 

 found in the spikes, bearing from ten to thirty double flowers, 

 and conversely. 



Lastly, hybridization shows that the seeds contain in them- 

 selves, unaffected by other conditions, the essence of what 

 will be manifested in the plant later on. It must be added 

 that there is in each variety a special tendency to produce 

 double or single flowers, as the case may be. There are 

 some which, however treated, never yield any but single 

 flowers, while others produce almost, or quite exclusively, 

 double flowers, and are, in consequence, doomed to disap- 

 pear. 



These results are so striking that we cannot but think our 

 great seedsmen will repeat the experiments in due season, 

 and avail themselves of the valuable information thus placed 

 at their disposal. — Gardeners' Chronicle. 



Entomology. 

 The Red Mite on Trees. 



T N the second number of this journal (p. 30) Professor A. .S. 

 ^ Packard has a note on " The Red Mite on Verbenas," in 

 which he describes the character of the injuries committed 

 by this minute insect, and gives a summary of the most effi- 

 cient remedies known. It is usually considered and spoken 

 of, by gardeners and horticulturists, as being most trouble- 

 some and injurious to plants in green-houses and conserva- 

 tories, and occasionally to shrubs, etc., growing in the open 

 air. 



With the exception of the two instances quoted below, I do 

 not know of any record of its injuries to large forest or shade 

 trees in this country. 



In Europe it is mentioned by several writers as attacking 

 the Linden. In "Economic Entomology, Aptei'a," by Andrew 

 Murray, those found upon the Linden are given under the 

 name of Tetranychus tiliartim, and they are said to "occasion- 

 ally occur in such numbers as almost to denude the trees of 

 their foliage." 



During the past summer, and also in 1887, I have found 

 these little pests attacking, and quite seriously injuring, the 

 foliage of large trees in the Arnold Arboretum, and on the 

 parks and streets and other places about Boston. 



The White Oak (Q. alba) seems to have suffered more than 

 any other, but all Oaks, both native and those that have been 

 introduced from foreign countries, have been more or less 

 attacked. Those trees with very smooth, shining leaves seem 

 to be least liable to injury, but by no means exempt, as the 

 foliage of Qucrcus rubra, Q. coccinea and others very often 

 showed too well. I liave found the mites living almost ex- 



clusively on the upper surface of the leaves of all the Oaks, spin- 

 ning a very slight web, which is almost invisible, but the 

 existence of which may be proved by brushing the leaf with a 

 camel's hair brush and thus accumulating the webs. In some 

 instances a few were foimd on the under side of the leaves, 

 but these seemed to be stragglers. 



The eftect of their work on the Oak is to give the foliage a 

 general dusty aspect, the leaves become yellowish or grayish 

 above, with lighter patches here and there, and they arb fre- 

 quently so much injured as to become twisted and turned, as 

 if scorched. On some Oaks, such as Q. palustris, the leaves 

 become of an even, dull, ashy color all over the upper sur- 

 face. 



It should be stated here that the blotched yellowish or 

 dusty appearance of the Oak leaves is not always entirely 

 produced by the red mite, but is very often caused, either 

 independently, or with the assistance of the mite, by a 

 hemipterous insect, Corythuca arcuata, which may be found 

 on the under side of the leaves, from which they suck 

 the sap with their slender beaks. The delicate wing-covers are 

 flat, meshed and scale-like, of a white color, with a dark band 

 across the base and another at the tip, Init the dark spots vary 

 in different individuals and are sometimes very faint or entirelv 

 lost. The body is black and the largest specimens are about 

 one-sixth of an inch in length. They usually feed in groups, 

 causing- the opposite upper side of the leaf to become gray or 

 yellow. On very many Elms the foliage has had a dustv, 

 grayish look, which, upon close examination, has proved to 

 be the work of vast numbers of the red mites living upon both 

 sides of the leaves, but, generally, most abundant on the lower 

 surface. 



They live chiefly on the under side of the leaves of the 

 Maple, which either turn an even yellowish gray or become 

 thickly dotted. 



They are to be found on the Linden, Ash, Locust and other 

 shade trees, and on the Apple, Plum, Cherry and Peach. The 

 amount of damage done to these trees has not g'enerally been 

 serious enough to attract much attention, but I have seen 

 vigorous young Plum trees lose all their leaves during 

 the month of August, entirely owing to the work of myriads of 

 red mites upon them. 



I have found them in large numbers on the American and 

 European Larches, on the Hemlock {Tsiiga Canadensis), and 

 also quite common on Arbor-vitag, Spruces, Junipers and 

 White Pines. The foliage of the Larch assumes a dead, 

 brownish appearance when seriously attacked, while the 

 leaves of the Hemlock liecome of a dull ashy or dirty white 

 color. 



In the American Entomologist and Botanist, Aj^ril, 1870 

 (Vol. 2), p. 180, Professor C. V. Riley says of the mite; "It is 

 best known in the green-house, but likewise does much dam- 

 age in dry seasons on trees (especially evergreens) in the 

 open air. It thrives best in a dry atmosphere, and we have 

 found no dilficulty in getting rid of it by a free use of its natu- 

 ral enemy — water. If a little soap is mixed with the water it 

 will be more effectual." 



In the "Fourteenth Report of the State Entomologist of 

 Illinois" (1884), p. 117, Professor S. A. Forbes says: "In June 

 tlie foliage of the Larches in the grounds of the University at 

 Normal, were seriously affected by the red spider (Tetranychus 

 telarius, L.), some of the trees seeming likely to die. On one 

 of those worst infested we tried the eftect of spraying with 

 kerosene emulsion made with soap and diluted to contain two 

 and one-half per cent, of kerosene. The insects were greatly 

 reduced in number by a single application, but not all killed. 

 The trees soon revived appreciably, as compared with those 

 not treated." 



In examining the mites on dilferent plants, I find that there 

 seems to be a marked variation in their color on some kinds 

 of trees and shrubs. In most cases they are of the typical 

 Ijrick red color, varying in intensity on dilferent plants as well 

 as in the age of the mites. These are usually described as 

 light yellow when young, becoming darker as they grow 

 older. 



Some of the Elms on Boston Common and the streets of 

 the citv were verv badly infested, and, in some cases, almost 

 completely defoliated, during the latter part of the summer, 

 by this or' a similar mite, which seems to be of a yellowish 

 green color in all stages of its growth. 



At least, on several young trees, from ten to fifteen feet in 

 height, which were literally swarming with nfites, so that even 

 the limbs and trunks were covered with their fine web, I was 

 unable to find any specimens of a decidedly red color. Those 

 found on the Butternut were also p;ile yellowish green. On 

 the White Ash [Fraxiniis Americana) they vary considerably 



