790 DOMATIA IN CERTAIN AUSTRALIAN AND OTHER PLANTS, 



it seemed considerably browner and thicker, in others again it 

 was not distinguishable from the plasma of cells which were not 

 covered with masses of excrement. . . . Tluough examination 

 of consecutive sections of an inhal>ited doniatium, I have proved 

 that the inner wall is quite unhurt, not injured by punctures or 

 bites " (1, p. 20). 



Again, under Lmorns nobilis : — " On a specimen about 2 met. 

 high wliicli I have kept six years in a room, and from which the 

 mites have been removed partly by smoke and partly by means 

 of a brush, the domatia have become by degrees indistinct, and 

 indeed liave quite disappeared from certain boughs. It has been 

 distinctly proved by this, that where mites are absent, there the 

 domatia have not attained their normal development and size, so 

 that the full development of the domatia is in necessary connection 

 with the presence of mites " (1, p. 49). 



By means of carefully planned culture experiments, he 

 attempted to prove; that the domatia only came after the arrival 

 of the mites, but partially failed, as the resulting plants did pro- 

 duce domatia, although fewer in number, smaller and poorer in 

 hairs than normally. On p. 61, he says it has been plainly proved 

 that the domatia in Psychotria, I'ilia, Laurus and others can only 

 reach their full development in the presence of mites, and that 

 these being absent, the domatia do not develop fully. 



After prolonged consideration of the subject, I cannot consider 

 Dr. Lundstrom's theory as perfectly explanatory of the use of 

 these structures, although I must acknowledge that I have no 

 better solution to offer. Some of the points which have occurred 

 to me as being against his view follow. 



The mites are not always to be found in wild plants; even when 

 the domatia are fully developed, they are often absent. Dozens 

 of domatia may he searched and no mites found. In examining 

 large numbers of leaves of PennatUia Cunninyhandi I found none 

 present in the earlier stages of the development, which is just the 

 time when their presence is needed. I tind them also in the rolled 

 leaves: such as Ricinocarpus pinifoliiis, and in the stomatal crypts 

 of Banksia, and they seem to be just as much at home there as in 



