BY ALEX. G. HAMILTON. 791 



the domatia. I have often seen them in cracks and crevices of tlie 

 plant, as between bud-scales, or in the chink between a petiole 

 and a stem, as has Dr. Lundstrom himself. But I do not think 

 that it is necessary to consider any of these places as dwellings 

 specially prepared for the mites. Indeed Dr. Lundstrom uses an 

 apt illustration of this very point when he says it would be as 

 reasonable to consider a wood where a hare was started as a 

 dwelling specially formed for the hare. The fact that the two 

 plants in which I found great numbers of mites had in the one 

 case diseased and in the other damaged domatia is very important, 

 especially as they were not the hurtful mites, but of the same 

 kind as those figured as domatia-dwellers. Again Dr. Lundstrom 

 takes the fact of the leaves containing most domatia being very 

 luxuriant in growth and very healthy as proving the benefit 

 derived from the mites. But is it not possible that the Acarids 

 might be attracted by those very states 1 



On the whole, therefore, while not denying the possibility of 

 Dr. Lundsti-iJm's view being the right one, I am of opinion (and I 

 set forth nn' opinion in opposition to that of so good an observer 

 with considerable hesitation) that the whole question needs much 

 further observation and research. The following points need 

 .special attention : — 



(1). The development of the tissues in all stages of the for- 

 mation of the organs. 



(2). The careful determination of the species of mites found in 

 each species of domatia-bearing plants (a) in a state of nature ; 

 (b) in plants cultivated in different countries. 



There also I'emains much to be done in the discovery of other 

 domatia-bearing plants, and in the habitat in which each is found. 



I should have mentioned that 1 ha^^e never been able to find 

 either in specimens or in figures of fossil leaves any appearance 

 of these structures. 



But Mr. Henry Deane informs me that from Gippsland he has 

 some fossil leaves of a Coprosma-like plant which apparently show 

 decided prominences in the principal vein-axils. As this is the 

 invariable situation of domatia in that genus it is not improbable 



