

i 



THE GENUS CHLOHOCHYTIUUM. 



27 



Plate 2. 



Representing the cell-walls o/CnLOROCHyxRiUM paradoxum. A1] figs. X 825. 



Fij^-s. 17 Sc 18. Cells -witli very nmdi tliickened walls bearing internal strinted projections. 

 Figs. 19-23. Cells destitute of internal thickeninn^s, showing great varialjilitj in form and 



size of the cell and in the shape and number of the external thickenings. 



Plate 3. 



Representiny cells of Chlorochythium paradoxum ; figs. 24-27 from living material, 



X 825; figs. 28--o0 from stained preparations^ x 1435. 



Fig, 24. Surface view of rapidly growing cell. 



Fig. 2o. Optical section of the same cell, showing the clear space produced by tlie large 



central pyrenoid (;?//,), surrounded by a small axis [a) of green protoplasm, from 



which radiate branched arms with ends expanded against the cell-wall. Owin^*' 



to extremely rapid growth, the parietal portions of the cJiloroplast have expanded 



to form thin irregular plates at one end of the cell. 

 Fig. 2^. Surface view of more slowly grown cell^ with apparently numerous, mure or less 



discoid, parietal chloroplasts. 

 Fig. 27. Optical section of the same cell, showing the central axis [a) of the chlorophist 



with numerous radiating arms, the expanded ends of which are closely pressed 



against the cell-wall. 



Figs. 28-30. Serial sections of a cell stained with Uelafield's htjematoxyliuj showing a large 



central pyrenoid with irregular starch-plates, a nucleus of considerable size con- 

 taining a large karyosome and a few achromatic granules, and a radiating 

 colourless cytoplasmic reticulum (dark), the meshes of which are occupied by the 

 branched radiating arms of the chloroplast, in which a fine cytoplasmic reticulum 

 can easily be seen. 28, tangential section near surface of cell; 29, middle section 

 through central pyrenoid ; 30, surface section showing ends of radiating branches 

 of chlorophist separated by colourless cytoplasmic reticulum. 



c. colourless cytoplasm, ch. chloroplast, /,;. Itaryosome, 7u nucleus,;)?/, pyrenoid, 

 fs.jj. starch-plates. 



An additional note on a form not originally included in the synopsis. 



The al^a tliat has been describod as ChlorocJiytrinni gUjeoplulum^ Bohlin, is 

 probably onl}^ a form of C, Fac€iolaa\ Bristol^ since tlie figures and description 

 given hy Bohlin, and more recently by Moore, make it quite easy to reconcile 

 the two. The habitat, and the size and form of the cells toirelher with the 

 nature of the cell-wall are quite comparable, while apIanosporc;s are produced 

 and set free in an exactly similar manner in both ''species.'' The absence of 

 iioogonidia in Bohlin'sform can be regarded as an effect of environment, and 

 it is possible that under suitable conditions zoogonidia might be produced 

 (cf. C. grande). Moore describes tlte cliloroplast as parietal, but liis 

 description is based apparently on the external appearance of the cell^ 

 whereas a considerable experience with tliese forms hus shown that it is 



