PARASITIC ENEMIES OF TREES AND PLANTS 



489 



growths are now known to the students of them, have 

 been described, and a very large number of them figured. 

 For instance, over fifty different galls occur on the 

 willow alone, and more than three hundred have been 

 listed for the oak. All these have received their techni- 

 cal, scientific names, and have been duly classified in 

 works on the subject 



In none of the several works before me do I find any 

 description of the galls that occasionally occur on our 

 well-known "black-eyed Susan" or cone-flower (Rud- 

 beckia hirta), an example of which I came across some 

 three years ago, in a meadow a few miles west of the 

 National Capital. Upon returning to my home I at 

 once made a life-size negative of the specimen, and a 

 print from it is reproduced in Figure i. The galls were 

 large, of a dark green color, shaped something like young 

 tomatoes, being bunched in groups of from two to four 

 on the extremities of the stems of the plant, where they 

 destroyed both flowers and leaves. 



While botanizing in the same city during the summer 

 of 1920, I discovered a remarkable specimen of trefoil. 

 The plant had a height of some four feet, and was in no 

 way crowded by the surrounding vegetation. Its remark- 

 able stem at once attracted my attention ; and I should 

 not have recognized its genus had I not observed that it 

 bore the well-known seed-pods of some species of tick 

 trefoil (Figs. 2 and 3). On the lower part of the plant 

 in Figure 2, quite a number of the leaves show very 

 well ; and their lanceloate form, taken in connection 

 with the form and structure of the seed-pods, the locality 

 and so on, it is quite possible that the species is Desmo- 

 dium bracteosum. Recognizing the very unusual condi- 

 tion of the plant, I collected it, or nearly as much of it as 

 would fully exhibit the pathology it presented, and made 

 the two photographs here shown. The specimen was 

 then taken to Prof. Paul D. Standley, the botanist of the 

 Smithsonian Institution, who pronounced the case to be 

 one of "hypertrophy ;" but he had never before seen 

 anything of the same character in tick-trefoil. He was 

 not quite certain as to the species, and declined to coni- 

 mit himself on that point. The specimen was accepted for 

 the collection representing plant pathology in the United 

 States National Museum. The superior extremity of this 

 specimen is shown in the reproduction of my photograph 

 in Fig. 2.; while in Fig. 3, we have the upper third of 

 the plant, almost down to a point where the disease com- 

 menced. This cut exhibits quite a number of the leaves 

 their form, number and arrangement to be taken into 

 account and considered. Gray points out in his botany 

 that in Desmodium bracteosum the character of the 

 species is that it is "very smooth except the pannicle; 

 stem straight ; leaflets lanceolate-ovate and taper-pointed, 

 green and glabrous on both sides, longer than the petiole, 

 the conspicuous bracts and stipules i 1.5 cms. long; joints 

 of pod rhomboid-oblong, smoothish." He figures the 

 pods, and they agree, as does the form of the leaves, 



with the corresponding parts in the specimen under con- 

 sideration. 



How this condition came about in a specimen of tick 

 trefoil would be difficult to say ; and surely it would ap- 

 pear, from what we know of such things, that it was 

 not from the puncture made by any parasitic insect. 

 That such happenings are worthy of record there can be 

 no question ; for knowledge of fact is knowledge, quite 

 irrespective of kind, and no one can predict as to when 

 it may prove of value. 



Doctor Howard presents us with two or three valu- 

 able and interesting chapters on the Gall-Fhes; the 



CURIOUS GALL ON OAK TREES 



Fig. 7 Several of these galls may sometimes be found on 

 the, twigs of the same limb, and they vary considera.bly in size. 

 The ones here shown are above the average in point of size. 

 Sometimes, as in the specimen here shown, this gall does not 

 seem to destroy the twig to which it is attached. 



Gall-Gnats, and the life history of a Gall-Gnat in his work 

 "The Insect Book." In speaking of those Cynipoids 

 known as Gall-flies, he says that "those which make galls 

 lay their eggs in the tissues of the growing plant and the 

 larvae, when hatched, feed upon the plant cells and their 

 contents. A very slight gall deformation may result; 

 but in the majority of cases there is a rapid growth of 

 plant-cells and a curious enlargement of variable shapes 

 which is called a gall. 



"The nature of a gall has long been a disputed point. 



