T^ 



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^ 



I ■ ■• 



THE GENDS CHLOROCIJYTBIUM 



5 



as to tlie shape and extent of the chlorophist or the natiire of the cell-contents 

 from the mere examination of living material; also the material stained In 

 bulk gave no results of any value. Hence carefully selected Lemna fronds 

 containing a large number of Chi orach f/trinm cells were fixed with Bouin's 

 solution, embedded in paraffin and cut into sections 5-10 /t thick. The 

 sections thus obtained were stained with Delafield's ha^inatoxylin or with 

 Heidenhain's iron-alum-haimatoxj lin and mounted in Canada Balsam. 



Sections prepared in this way show tijat the endophytic cells are situated 

 in the intercellular spaces of the liost-plant, and are possessed of a firm 

 cellulose cell- wall varying in thickness from 1-1'5 /^. Only very occasionally 

 were the cells cut through in such a manner as to show the tubular pro- 

 longation of the wall (see Tl. 1. fig. 1), and in no case was a cellulose button 

 found at the end of the tube. The cells in some cases are sub-spherical or 

 ellipsoid, but in others quite irregular, evidently from tlie pressure of the 

 surrounding tissue of the host. Each contains a single more or less centrally 

 placed nucleus, bounded by a nuclear membrane and containing a large 

 karyosome; in some cases a few granules could be seenin the nuclear space, 

 but these did not seem to be of a chromatic nature. 



, From serial sections it has been possible to reconstruct the internal structure 

 of the cell, and the examination of a number of cells has shown that, though 



the chloroplast is always built up on the same principle, yet it is subject 

 to so much variation in individuals that there is little wonder that it has 



been described so variously in the past. 



(1 



radial sections of fairly typical specimens taken through the nucleus. From 

 these it is seen tliat there is a single chloroplast consisting of a small central 

 mass surrounding the nucleus, and a varying number of radiating branches 

 which spread out on reaching the periphery of the cell and flatten the 



i^mseives 



1 



against the cell-wall. In many cases these parietal portions seem to be fused 

 together so that from the outside there appears to be a more or less 

 continuous parietal chlorofdast with internally projecting ledges or rods^ as 

 described by Klebs and Wille. That this is probably not the case is shown 

 in fig. 7 where several of the parietal portions of the chloroplast are quite 

 separate from one another, and in fig, S where there is no fusion at all It 

 must have been a preponderance of cells in this condition that led De Toni to 

 describe them as containing disc-shaped chloroplasts- 



Again, individuals were found such as those represented in figs. 9-11^ in 

 wdiich the central portion and the radiating branches of the cldoroplast were 

 very much reduced and the parietal portions correspondingly developed, so 

 that there appears to be astonishingly little difEerence between the chloro- 

 plasts of these particular cells and the truly parietal chlorojjlast figured by 

 Freenum"^* for Cldorochytrium inclusum. On the other hand, it can be seen 



-p 



* Freeraaiij E. M. '' Observations on Chlorochytriumy Minnesota Hot. Stiulio.^jj vol. ii 

 Part 111. 18D8(?). 



