CCxii PKOCEEDINGS OF THE ROYAL HORTICULTURAL SOCIETY. 



extra nourishment and a compensatory distribution of sap. {Origm of 

 Plant Structures, p. 59.) 



Four-spiked Typha. — Dr. Masters showed a specimen, from Mr. 

 Smith, Newry, in which the stem bore four free terminal inflorescences, 

 but it was not clear whether they were due to cohesion or fasciation. 



Boot-galls. — Dr. Masters exhibited some globular galls on the root 

 of an Oak. (Fig. 344.) Mr. Saunders said they were caused by the grubs 

 of one of the hymenopterous gall-flies, known as Tcras terminalis, a fly 

 that may be bred from the common Oak galls, generally known as " Oak 

 Apples," but they produce flies known as Biorliiza aptera. This apparent 

 anomaly is accounted for by the fact that among these hymenopterous 

 gall-flies the cycle of the insect's life is not completed in one generation, 

 in many instances but two generations are necessary, one in which there 

 are both males and females, the other in which there are only females. 

 This very curious fact was first demonstrated by Dr. Adler, of Schleswig, 



IK. 



Fig. 344. — Galls ox Roots produced by Cynips (Biorhiza 

 aptera). (Gardeners' Chronicle.) 



after some very interesting experiments made by him in breeding these 

 flies. The insects w^hich emerge from these root-galls are spoken of as 

 flies, but they are wingless ; they are about of an inch in length, and 

 have the appearance of ants. This generation is composed entirely of 

 females ; they climb up the stems of the Oaks, and make their way 

 generally to the buds at the ends of the shoots, into which they insert a 

 large number of eggs. When the grubs are hatched their action in feed- 

 ing oil the contents of the bud causes it to assume the familiar shape of 

 the Oak Apx)le, which, if cut open at the proper time, will be found to 

 contain a number of cells, each tenanted by a grub. When the insects 

 have undergone their transformation within these cells they emerge from 

 the galls, and this generation consists of both males and females ; the 

 former are winged, but the females are not. These females descend the 

 trees and make their way to the roots in which they deposit their eggs, 

 the grubs from which form galls, and so the existence of this species goes 



