INTRODUCTION. 9 



however, that it is not each individual spore which is 

 fertilized, as is the case in seed-bearing plants ; but that 

 the fertilizing influence is imparted to the pistil, or spo- 

 rangium itself, when that body is in its most elementary 

 form, long before any spore is produced in its substance, 

 and even when it is itself scarcely to be distinguished 

 from an ordinary cell. Antheridia, as the supposed fer- 

 tilizing organs are called, are most readily seen among 

 the Fucacea." 



After describing a second mode found only among the 

 simpler kinds, where the whole body consists of a single 

 cell, Dr. Harvey proceeds : — " The third mode of con- 

 tinuing the species has been observed in many Algse of 

 the Green series, in some of which sporangia are also 

 formed, but in others no fructification other than what 

 I am about to describe has been detected. This mode 

 is as follows. In an early stage the green matter, or 

 endo chrome, contained within the cells of these Algse, 

 is of a nearly homogeneous consistence throughout, and 

 nearly fluid ; but at an advanced period it becomes 

 more and more granulated. The granules, when formed 

 in the cells, at first adhere to the inner surface of the 

 membranous wall, but soon detach themselves, and float 

 freely in the cell. At first they are of irregular shapes, 

 but they gradually become spheroidal. They then congre- 

 gate into a dense mass in the centre of the cell, and a 

 movement, aptly compared to that of the swarming of 

 bees round their queen, begins to take place. One by 

 one these active granules detach themselves from the 

 swarm, and move about in the vacant space of the cell 

 with great vivacity. Continually pushing against the 

 sides of the cell-wall, they at length pierce it, and issue 

 from their prison into the surrounding fluid, where their 



