PLATE IV. 



Cross section ol" an as yet uninhabited petiolar swelling of a young TachigaUa. 

 showing the intact nutritive parenchyma, laige pith cavity, and thin layer of 

 pith cells lining: it. Photograph by Prof. I. W. Bailey. 



Cross section of a petiolar swelling inhabited by Coccidotropkiis socialis, show- 

 ing the gnawed nutritive parenchyma and the frass ridges. Photograph by 

 Prof. I. W. Bailey. 



Section similar to that of Fig. 2 but showing three Cncddofrnphus 

 cross section. Photograph by Prof. I. W. Bailey. 



