11 



outwardly the palisade branches. "J^hese branches are 

 several times the breadth of the hypha from which they 

 arise. Each has a narrow base, its cavity sometimes 

 separated from the hypha by a partition. More commoiily 

 the partition occurs on the hypha itself just before the 

 pahsade process is given off. The palisade " cell " rapidly 

 thickens, and finall}^ ends in a swollen rounded head 

 (PI. I., fig. 3), or more commonly, retains a uniform 

 diameter for the upper third of its length, and ends in a 

 bluntly rounded manner. The apex is in many cases 

 quite smooth, but in other cases is distinctly mucron- 

 ate. The wall of the cell at the apex is much thicker 

 than elsewhere, especially so at the extreme tip. The 

 palisade cell contains protoplasm distributed in a thin 

 layer over the wall, with fine strands traversing the 

 cavity. Towards the apex, however, the protoplasm is 

 more abundant, and finall}^ becomes aggregated in a non- 

 vacuolated mass just at the apex itself. The chloroplasts, 

 which are very numerous, are collected into a dense 

 layer or mass, just at the apex, but occur also scattered 

 in rows and clusters in the peripheral protoplasmic layer. 

 On teasing out a portion of a very young plant, one is 

 able to see the relationship of the medullary hypha and 

 the lateral processes more clearly. Figure 11, PI. II., 

 shows the terminal portion of a superficial medullary 

 hypha, which has given off a lateral " palisade cell," now 

 nearly mature, and which is forming two lateral processes 

 acropetally, destined to become "palisade cells." It will 

 be observed that the thickenings or septa are formed very 

 early, and behind the point of origin of each process. 

 Figures 10 and 14 show two septa in an older filament. 

 The wall is double, and the septum is seen to be due to 

 secondary deposit on the inner layer. For a long time 

 protoplasmic continuity is maintained ; indeed, it was 



