14 INTRODUCTION. IV. 



cult of observation. At length, among the highest Algse we encounter what appear 

 to be really two sexes, one analogous to the anther and the other to the pistil of 

 flowering plants. It would seem, 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 sporangium 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 fertilizing organs are called, are most readily seen among the Fiicacece, 

 and will be described under that family. 



Besides the reproduction by means of proper spores, many Algte have a second 

 mode of continuing the species, and some even a third. Among the simpler kinds, 

 where the whole body consists of a single cell, a fissiparous division, exactly similar 

 to the fissiparous multiplication of cells among higher plants, takes place. This cell, 

 as has been already mentioned, divides at maturity into two parts, which, falling 

 asunder, become separate individuals. Similar self-division has been noticed among 

 the lower Palmellacece, and in other imperfectly organized families. Such a mode 

 of multiplying individuals is analogous to the propagation of larger plants by the 

 process of gemmation, where buds are formed and thrown off to become new indivi- 

 duals. When, as in the Lemna or Duckweed, the whole vegetable body is as simple 

 as a phanerogamous plant can well be, the new frondlets or buds are produced in 

 a manner very strikingly analogous to the production of new fronds in Desmidiacece. 



The third mode of continuing the species has been observed in many Algse of the 

 green series, in some of which sporangia are also formed, but in others no fructifica- 

 tion other than what I am about to describe has been detected. This mode is as 

 follows. In an early stage, the green matter, or endochrome, contained within the cells 

 of these Algse, is of a nearly homogeneous consistence throughout, and semi-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 congregate 

 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 seemingly spontaneous movements are continued 

 for some time. These vivacious granules, or zoospores as they have been called, at 

 length become fixed to some submerged object, where they soon begin to develop 

 cells, and at length grow into AlgaB similar to those from whose cells they issued. 



Their spontaneous movements before and immediately subsequent to emission 

 lead me to speak of the 



MOVEMENTS OF ALG^ 



in genei'al. These are of various kinds, and of greater or less degrees of vivacity 



