12 



of M-liat ap])ears to be coao-alated cytoplasm. The struc- 

 tiuo of tlie ])it will be referred to again, when discu.ssino- 

 the histology of the shoot subseciueiitly. 



Connected with the central elongated cells of the con- 

 dncting tissue are the Collecting Cells. These are much 

 shorter than the central cells, and as we pass further out 

 they diminish still more in size. They form a lather 

 closer tissue than the conducting cells, and they are 

 extensively connected by pits, with or without the above- 

 mentioned protoplasmic caps, with any of the neighbour- 

 ing cells they may come into contact with. The nearer 

 we come to the outside the more regularly do they come 

 to lie in rows. Finally there arise from them the very 

 regular rows of Assimilating Cells, which run parallel to 

 one another, but are curved upwards and outwards at a 

 certain very definite angle with regard to the longitudinal 

 axis of the whole shoot. The assimilating cells possess 

 numerous pits, which are however all destitute of caps. 



The whole body of Chondrus crhjms consists of a com- 

 plete system of veiy long and very much branched liyphse. 

 The assimilating cells f()]'ni the a])ical branches of these 

 liyplne. As a general rule the divisions in these threads 

 Avill take place at right angles to the longitudinal axis 

 of each cell row. l^ut there is evidence to sIioav that some 

 of the divisions are more or less at rio-ht ano-les to this 

 direction. Hyphal tissue of this kind has been distinguished 

 as plectencliyma. The iilamentous nature of the tissues 

 l)ecomes very apparent if the growing point of a frond is 

 examined in a longitudinal section, when one can see 

 spreading out in a fan-shaped fashion the hyphte of all the 

 three tissues (PL IL, tig. 6). 



In transverse section the cells of a young plant differ 

 little in appearance from what is seen in longitudinal 

 section, except that the conducting cells appear rather 



