384 



ORGANOGRAPHY. 



and they are even described hj some authors, as Berkley, as mo- 

 noecious or dioecious. In these Algae also, the reproductive organs 

 seem to be, as in the last sub-order, of three kinds : — namely, 

 1, zoospores] 2. spores \ and 3. antheridia. 



1. The zoospores are found either in large numbers, in peculiar 

 cells called oosporangia, sjyorangia, or commonly spores, which 

 are placed at the articulations {fig. 839), or summits of the divi- 

 sions of the frond ; or singly, in each cell of a jointed thread-like 

 body, which has been called the irichosporangimn. These zoo- 

 spores have essentially the same structure as those previously 

 described in plants of the sub-order Chlorosporese ; that is, when 

 discharged from their sporangia, they have no cellulose coat, 

 but consist merely of a protoplasmic sac furnished with cilice, by 

 which they actively move for some time ; 

 Fig. 839. they then become immovable, acquire a cellular 

 coat, and germinate. The zoospores of the 

 trichosporangia appear to be closely allied to 

 the spermatozoids. The zoospores are of an 

 olive-brown colour, somewhat pear-shaped, and 

 have but two ciliae of unequal length diverging 

 from each other. The zoospores are not true 

 generative spores, but gemmce or buds. 



2. The Spores, or inactive spores as they 

 may be called in contradistinction to the zoo- 

 spores, on account of their being motionless, are 

 situated in sacs called sporangia {fig. 840, sp) or 

 perispores. In rare cases but one spore is con- 

 tained in each sporangium or perispore. as in 

 Halidrys, but generally the sporangium divides 

 in such a manner as to form a cluster of eight 

 spores or sporules, which is therefore termed an 

 Fig 839 Portion of octospore. Besides the perispore, the spores are 

 a filament of Ecto- also enclosed in two other membranes, one situ- 

 hl-irmgTXJxT'oo- ^^^^ directly within it, called the epispore, and a 

 sporangia or svores; third internal to the latter. The oetospores ulti- 

 termed °lm!^s*por^e7. Tti3,tely decay unless fecundated by antherozoids, 

 After Henfrey. " hence they are the true generative spores. 



These sporangia are either dispersed all over 

 the surface of the frond ; or they are collected in definite groups 

 called sori on its surface ; or on the walls of globose cavities 

 called conceptacles or scapkidia {fig. 840), which communicate 

 with the external surface by a pore, s. These conceptacles are 

 usually grouped together in somewhat club-shaped or oval recep- 

 tacles, situated at the summit or side of the frond or its divisions 



{fig. 7, t). 



3. The Antheridia are little, usually somewhat ovate sacs 

 {fig. 842, a), attached to delicate jointed filaments arising from 

 the inner surface of the conceptacle {fig. 840). The antheridia 



