774 DOMATIA IN CERTAIN AUSTRALIAN AND OTHER PLANTS, 



The mites were the same species as are usually found in domatia. 

 They appear to be very near, if not identical with, the Gamasus 

 fi<,'ured by Lundstrom. There could not be any doubt but that 

 the mites had an injurious effect, and this, with another case to 

 be referred to, was the only instance I have seen of the little 

 animals being hurtful to the plant. But there was no sign of the 

 peculiar alterations and structures which are caused by Fhytoptus 

 and some other noxious mites. 



Tarrietia actinophylla, C. Moore. — The leaves are digitately 

 compound, and when young are studded with star-shaped peltate 

 hairs, especially on the midrib. The domatia are in the leaflets 

 in the axils of the secondary veins and the midribs. They do not 

 occur in the lower part of the leaflet nor near its tip. In the 

 same leaflet some veins are in pairs opposite, and others alternate; 

 the domatia thus are in pairs or single. In three leaflets examined 

 by me there were 14, 15 and 17. The leaf is strong in texture 

 and smooth, shining on the upper surface, but not varnished. It 

 wets readily on this side, but on the lower surface the water runs 

 together and passes down the vein channels; it does not, lioweAer, 

 enter the domatia, as the orifice is too small. The pits are formed 

 by a widening of vein and midrib running out towards each other 

 and almost meeting in the centre (fig. 15), thus forming a depres- 

 sion leading into the domatium. Sometimes, however, the ridges 

 meet, and then the mouth is circular. I hav^e, therefore, put this 

 form in Group i. although it really is transitional between 

 1. and ii. The thickened part is lighter in colour than the rest of 

 the under side of the leaf. There are no stomata on the upper 

 surface, but they are plentiful below and of small size. None are 

 found in the interior of the domatium. The latter are 1-2 mm. 

 in diameter. Vascular bundles are plentiful in both walls and rim. 

 The interior is lined with stiflF hairs like those of Coprosma, the 

 points all being directed to the orifice. Acari were observed in 

 the domatia. The layers in a section of the pit were as follows: — 



(1) A rather thick cuticle. 



(2) The epidermis, the cells thick-walled and with bright brown 

 contents which give the tannin reaction faintly with ferric chloride. 



