Holloway. — TJk Prothallus and Young Plant of Tmesipteris. 23 



embryo. Longitudinal sections through the point of attachment of a young 

 plantlet to its parent prothallus. such as that shown in tigs. 58 and 59, and 

 in Plates II and III, in all of which the plant-axis is in transverse section, 

 hut the foot in longitudinal section, reveal the fact that the region of the 

 plantlet which is m immediate contact with the prothallial tissues— i.e., 

 the " foot " or absorbing region is prolonged into a large number of long 

 haustoria-like processes, which penetrate the tissues of the prothallus and 

 evidently function as absorbing organs. These processes are generally two 

 cells wide at their base, whilst the forward end of each is prolonged info a 

 row of single cells, the terminal cell of the row being more or less elongated 



Fig. 58. — Transverse section of young plantlet through point of attachment 

 to prothallus. showing foot and haustorial outgrowths. X- 42. 



and rounded. They emanate, appearing in section like the fingers of a hand, 

 from a region which consists largely of cells which are dividing. The cells 

 both of the processes and of the region from which they arise stain very 

 conspicuously with haematoxylin both in their walls and nuclei. In trans- 

 verse section the processes are circular in outline. This will be seen in 

 fig. 60, which also shows the nature of the surrounding prothallial cells. 

 On the side towards the plant-axis the cells gradually increase in size, and 

 median sections through the whole plant-foot reveal the fact that vascular 

 tissue, both xylem and phloem, extends from the plant-axis into the foot. 

 In fact, longitudinal sections of detached plantlets of similar age such 

 as that shown in fig. 68 indicate that the entire vascular bundle of the 

 young plant inclines at an angle into the foot. The obvious explanation 

 would be that at an early stage in the development of the young plant 



