FUNGOUS ROOT-TUBERCLES* 101 



EXPLANATION OF PLATES. 





All of the figures were drawn with the aid of a camera 

 lucida. A Leitz 1/12 oil immersion objective and ocular no. 

 4, giving a magnification of 1350 diameters, were used for all 

 except figures I, 14, and 29, for which use was made of a no. 

 3 objective and no. 1 ocular, giving a magnification of 85 

 diameters. 



Plate 6.— A portion of a Ceanothus root with many young tubercles 

 on the small lateral roots, above. Part of a Ceanothus root on which 

 older tubercles are formed into loose clusters, below. 



Plate 7. — A large Elaeagnus root showing the dense mass of tuber- 

 cles attached to it by a short branch, above. A portion of a root with 



large clusters, below. 



Plate 8.— Part of a stem of Myrica cerifera showing the masses 

 formed at the ends of short adventitious roots. , 



Plates 9-10.— Ceanothus americanus. 1, Transverse section of a 

 root tubercle of Ceanothus indicating the infected region and some of 

 the fungal stages. 2, Cells of the meristematic region showing early 

 stages of infection. One cell shows where a hypha is just entering. 

 The cell wall between some of the cells is being dissolved. 3, An 

 embryonic cell just infected showing the branched mycelium. 4, An 

 older hypertrophied host cell with enlarged nucleus. The mycelium 

 is much branched and entwined. No vesicles have yet been formed; 

 portions of the cell walls are being dissolved. 5, 6, Nuclei of the 

 fungus set forth by the haematoxylin stain. The hyphal walls are 

 difficult to differentiate. 7, A stage where the sporanges are formed 

 at the end of the hyphal branches. Infection of adjoining cells is also 

 shown. 8, Hypertrophied nuclei of the host cell differing from the 

 following. 9, Nuclei of digestive cells similar to the one shown in 

 f. 7. 10, Young sporanges showing their content. 11, Older and 

 mature vesicles with a single nucleus. 12, Sporanges burst open, the 

 content has disappeared. 13, A cell showing the last stage of the 

 fungus where all but the walls of the mycelium is absorbed. 



Plates 10-12.— Elaeagnus argentea. 14, Cross section showing the 

 infected region of the tubercle and its various tissues. The large 

 dense cells contain the fungus in the vesicular stage,— other cells 

 show younger stages. 15, Two uninfected cells showing nucleus, 

 large starch grains and fine granular cytoplasm. 16, An infected cell 

 showing hypertrophied nucleus, the mass of mycelial threads and the 

 mode of infection. 17, 18, Infected cells where the hyphae pass 

 through the cell wall into adjoining cells. 19, A large hypertrophied 

 cell with an amoeboid nucleus. The fungus has the sporanges, in 



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