108 Mr. W. Gardiner. The Histology of the Cell Wall, 



Fig. 4. 



t ft 



numerous small isolated groups of wall-threads are present on the 

 side walls, and a large group occupies each end wall. In certain cells 

 both "pit-threads" and "wall-threads" may simultaneously be 

 present. The method gives equally good results with thin or thick- 

 walled tissue, and in the case of the thinnest walls an " en face " 

 view can be obtained where a sectional view fails. The threads vary 

 in size. They are, for instance, exceedingly thick in Viscum album, 

 where they are seen with the greatest ease ; they are well developed 

 in Phaseolus multiflorus and Lilium martagon, and they are fine and 

 delicate in Aucuba japonica (fig. 5). The connecting threads may be 



Fig. 5. 



observed equally in the epidermis and cortex, and in all the living 

 cells of the tissues of the central cylinder. In a section of any given 

 tissue, it can be readily seen that all the cells are placed in commu- 

 nication with one another. One is tempted to expatiate upon the 

 wonderful beauty of the appearance presented by the walls studded 

 with their pits, each pit with its closing membrane traversed by the 

 thread complex after the manner of sieve-tubes. It is indeed a 

 sight which cannot fail to convey a lasting impression of wonder and 

 surprise. 



The pit-threads of such pulvini as were examined presented no 

 striking difference, either in appearance or distribution, to the 

 similar structures in ordinary tissue, and the same appears to be 

 true of the sieves of tendrils. The important point, however, is this, 



