of Chloroplasts and Leucoplasts . 99 
thallus, chloroplasts and all other contents of the cell present conclusive 
evidence of disorganization. 
It is, however, in the mucilage-producing hairs borne by the ventral 
scales and springing from the floor of the gemma cups, and in the young 
rhizoids, that chondriosomes find their greatest development. The large 
mucilage hair (Fig. 5, a) presents the usual structure of such cells at that 
age. In the rather dense cytoplasm the numerous rods and granules are 
strikingly conspicuous. Many of the rods are long, exceeding the greater 
diameter of the nucleus. Some of the rods show clearly that they consist 
of a row of very small granules. In the younger mucilage hair (Fig. 5, b) 
the cytoplasm is very dense, and the chondriosome primordia are smaller. 
There are no chloroplasts in the larger hairs, and in the youngest all 
staining bodies distinguishable in the uniform groundwork of the cytoplasm 
are minute. Whether chloroplast primordia are present here, I am not able 
to say with certainty. The cells of the young ventral scales bearing such 
mucilage hairs show the usual chloroplasts and chondriosomes, which are 
clearly and sharply differentiated. 
Perhaps one of the most striking parts of the thallus is seen in the 
young rhizoids (Fig. 9). The chondriosomes are very large and extremely 
numerous. In thick sections the whole cell seems to be filled with the blue 
or black rods and granules. These rods and granules show the character¬ 
istic division stages. No recognizable chloroplasts are evident at this stage 
of the hair’s development, although the cells of the ventral epidermis, from 
which the hairs develop, contain chloroplasts. Whether any of the bodies 
shown in Fig. 9 are disorganizing chloroplasts I am unable to state. As 
the rhizoids mature, all cell contents gradually disappear. 
The mucilage hairs arising from the base of the gemma cups and in 
the antheridial cavities do not contain chloroplasts but very numerous 
chondriosomes, although these are smaller than in the mucilage hairs borne 
by the ventral scales and by the young rhizoids. 
The methods of fixing and staining used here bring out clearly the 
progress in the formation of mucilage or slime in the so-called mucilage¬ 
bearing cells of the thallus of Marchantia . The mass of slime first appears 
in the centre of the cell. It presents a very fine, uniformly granular 
appearance, staining a greyish, bluish, or brownish colour, depending upon 
the intensity of primary staining with the haematoxylin or violet and the 
counterstain with the orange G. As the mass of mucilage increases, the 
cytoplasm, together with the nucleus, chloroplasts, and chondriosomes, are 
crowded into a thin layer along the cell wall. The entire living content of 
the cell is finally used in the formation of the slime. 
The mucilage excreted by mucilage hairs in both gemma cups and 
antheridial cavities, for example, seems to be of quite a different com¬ 
position. In the latter case, no trace of mucilage can be seen inside these 
H 2 
