Freeman : observations on chlorochytrium. 201 



on the lower surface while rather few are found on the upper 

 side. The following figures are taken from a medium-sized 

 frond in the peripheral region : on the under side 140-160 

 (sometimes as many as 230) in one square mm. ; on the upper 

 surface 60-65 in the same area. Many areas of 4 square mm. 

 on the upper surface contained no endophytes. 



The endophytic cells are found almost exclusively in the tis- 

 sues just beneath the pseudoepidermis of the nurse plant, with 

 the slightly pointed cmd just at or just below the surface. They 

 occur in rare cases in the central part of the frond completely 

 enclosed. The pointed ead protrudes from the tissues of the nurse 

 plant in but few cases and then not moij than for a distance 

 equal to one-half the thickness of its outer wall. The cells not 

 infrequently occur between the paraphyses of the nemathecia 

 of Constantinea where they usually penetrate to but not into the 

 tissues beneath. 



The predominant form assumed by the endophyte is pear- 

 shaped with the smaller end directed toward the surface of the 

 nurse plant. The cells are often ovoidal and even ellipsoidal. 

 In the central portion they assume a spheroidal form. In the 

 paraphyses they become elongated or assume a figure-of-eight 

 form similar to that described by Wright for Chlorochytrium 

 cohnii. The inner ends of the cells are marked more or less 

 b}'^ the bulgings undoubtedly caused by the pressure of the 

 adjacent cells of the nurse plant. 



The cells average 85-115 mic. in length and 40-85 mic. in 

 breadth but often attain 143 x 100 mic. The wall in some cases 

 is 28 mic. thick at the outer surface and 8 mic. thick around the 

 remainder of the cell, but usually is less than one-half of these 

 dimensions. The lamellation of the cell wall can clearly be 

 seen in many sections (especially glycerine mounts) and is due 

 probably to the apposition of successive layers of cellulose. 

 Chlorophyll occurs in the form of a single yellowish-green plate 

 in which are included a large number of fine refringent gran- 

 ules. This chromatophore extends around the entire wall of 

 the cell and contains a var3ang number of very conspicuous 

 pyrenoids, which are flattened spherical in form, 5-1 1 mic. in 

 diameter, and jut out into the cavity of the cell. As many as 

 thirty-nine have been found in a single cell and at least one 

 pyrenoid can be seen soon after the cell begins to penetrate the 

 tissues of the nurse plant. The pyrenoids show a clear central 



