BY ALEX. G. HAMILTON. 777 



than any I have seen in other plants; (4) close spongy paren- 

 chyma; (5) epidermis; and (6) cuticle. Here and there in the 

 spongy parenchyma occur spherical interspaces of large size and 

 destitute of contents. In the diseased-looking domatia of great 

 thickness I found that the spongy parenchyma layer was of 

 greater thickness, the hairs absent, and the roof and floor 

 epidermal cells filled with a red substance which formed a thick 

 layer on both roof and floor. I fancy that this diseased state is 

 caused by some insect (not a mite'; taking up its abode in the 

 domatia as I repeatedly found remains in sections of some rather 

 large insect. The mites were found in a few of the domatia, and 

 in all the domatia were found dust, pollen grains, and both spores 

 and mycelium of fungi. It is rather remarkable that these should 

 be so plentiful, as from the mouth opening towards the apex of 

 the leaf, and the leaf itself having a horizontal position, they 

 could scarcely be washed in by rain, especially as they are on the 

 under side of the leaf. I did not find such quantities of foreign 

 matter in any other domatia, even of those with orifices as large. 

 But Dr. Lundstrom notes the same kind of thing in many species 

 examined by him. 



Cedrela australis, F.v.M. — The domatia are like those of the 

 last plant, but flatter; stomata occur in the inside and there are 

 none of the spherical intercellular spaces mentioned above. 



In very young leaves (10 x 1-5 mm.) the under side of the leaf 

 is covered all over with hairs; as the leaf grows older, the hairs 

 drop off, except those in the axils where domatia are to form. 

 The hairs are of two kinds, pointed and thin, and short 4-celled 

 hairs filled with bright brown matter. These persist for some 

 time on the general leaf surface, and in the axils. They are 

 probably colleters. In a leaf 10x3 mm. I found the hair tufts 

 and a slight widening of the veins in the axils, and in larger-sized 

 leaves the tissue widens progressively. But the domatia have 

 not reached their full development even when the leaf is full 

 grown as to size. It is only when the leaf has gained its mature 

 hardness and consistency that the process of growth in the 

 domatia is complete. 



