352 Transactions. — Botany. 



garded these pits as coming under the head of " domatia," 

 and discussed four interpretations that might be put upon 

 them : (1) They may be pathological ; (2) they may have only 

 an indirect connection with their tenants ; (3) they may be for 

 catching insects ; (4) they may be of use to the plant as the 

 dwellings of commensals. He adopts this last interpretation 

 regarding the pits as being the result of a symbiosis between 

 the plant and minute Acarids, which are supposed to make 

 them their homes. He appears to have always found Acarids 

 in possession of these cavities. Mr. Hamilton says that as 

 often as not he found no mites there, and in two instances in 

 which he found large numbers of them the pits were damaged 

 by their presence. In these damaged pits he found "brownish 

 patches here and there, and also in places a number of the 

 cells were of a bright-crimson colour." I have avoided calling 

 these pits "domatia," for they do not seem to me to come 

 within the definition of such as given by Dr. Lundstrom — i.e., 

 " those formations or transformations in plants adapted to the 

 habitation of guests, whether animal or vegetable, which 

 are of service to the plant." 



In all the species of Coprosma I examined I found not a 

 single trace of an Acarid in the pits. As some of these species 

 were obtained from the Christchurch Botanical Gardens, or 

 from private gardens, I thought that this might be accounted 

 for by the fact of their not growing naturally in the bush ; but 

 in specimens obtained from the bush at Dunedin I found the 

 same state of affairs. In several of the species the tissues 

 round the pits were in an unhealthy condition, with brownish 

 patches here and there, and some cells of a bright-crimson 

 colour, just as described by Mr. Hamilton. There were, how- 

 ever, no Acarids present in such pits. I invariably found in 

 these cases what appeared to be the hyphae of some fungus 

 growing between the cells of the leaf-tissue. The crimson 

 cells were round in outline, and looked very much like spores, 

 and some seemed to be in the act of germinating. In 

 the cavity of the pits I frequently found quantities of 

 dust or other foreign matter collected, as did also 

 Dr. Lundstrom. The unhealthy state of the pits seemed 

 to me to be due to the attacks of some fungal parasite. 

 The cells of the leaf between which the hyphae grew were 

 not at all swollen or distorted. The unhealthy condition, too, 

 was by no means confined to the tissue around the pits, but 

 occurred in all parts of the leaf, so that it could scarcely have 

 been due to the presence of Acarids in the pits, though, of 

 course, the injurious effect of such presence would tend to 

 overthrow Dr. Lundstrom 's theory as to their utility to the 

 plant. As these mites appear to take refuge in any suitable 

 cavity (Mr. Hamilton found them in l'olled leaves of Eicino- 



