Aphanochdstacese 



313 



the base, which never possessed a chloroplast and early lost their scanty 

 protoplasmic contents ; they are entirely unseptate, very fragile, and, in all 

 except living plants examined with great care, they are broken off near the 

 base. In the lumen of the bristle there are often plug-like masses of some 

 refractive substance which give the bristle the appearance of being indis- 

 tinctly articulate. As Fritsch ('02) has shown, staining with Congo red 

 proves that these plugs are not transverse walls. 



Each cell contains a massive parietal chloroplast, generally with a 

 conspicuous pyrenoid and numerous small starch-grains. 



Asexual reproduction takes place by zoogonidia of which one to four are 

 produced in a mother-cell, the wall of which ruptures and sets them free. 

 They are variable in size, quadriciliated, and with a pigment-spot. On 



Fig. 205. Aphanochsste repens A. Br. A, plant with sexual organs, showing epiphytic habit. 

 B, escaped quadriciliated oosphere (the circumscribing line represents the extent of a delicate 

 mucous vesicle into which it is at first extruded). C, quadriciliated antherozoids. D, fertili- 

 zation of oosphere by antherozoid. All x 600 (after Huber, from Wille). 



coming to rest they develop unilaterally into a new plant. Aplanospores 

 are also formed singly from the vegetative cells (G. S. W., '04). 



The sexual reproduction of Aphcunochsete was investigated by Huber ('92), 

 and is of great interest on account of the clear differentiation of both sexual 

 organs and gametes. The oogonia are formed from some of the more central 

 cells of the thallus which are devoid of seta?. These cells grow in size, 

 assume a globular form and become loaded with starch and oil (figs. 205 A 

 and 206 oo). Only one spherical oosphere is formed within the oogonium ; 

 it is quadriciliated and escapes from the oogonium into a delicate hyaline 

 vesicle by the rupture of the upper portion of the wall (fig. 205). The 

 antheridia are developed at the extremities of the branches ; they are often 



