GuilHermond - Atkinson 



108 



Cytoplasm 



organelles, differing only slightly from the chondriosomes. Fur- 

 thermore, the chlorophyll and fucoxanthin disappear in the mother 

 cell of the antheridium and the phaeoplasts in this cell come to 

 look like chondrioconts and are distributed among the antherozoids 

 in such a way that each encloses a single phaeoplast. This plastid 

 later is filled with a carotinoid pigment and becomes the stigma. 

 The stigma, then, is simply a structure derived from a phaeoplast. 

 Plants in which the chlorophyll does not persist but rather 

 disappears in the sex organs are found in the Rhodophyceae (Flo- 

 rideae) and the Characeae. In the Rhodophyceae, for example in 

 Lemanea, the cells of the thallus (Fig. 78, I and the upper portion 

 of A) enclose large, ribbon-shaped rhodoplasts, sometimes anasto- 



o 





s^^n 



80, 



^ 



p.p. 



i.t. 1, 1, 1,1 . I.I. 1, 1. 1 



o to a o ^ 



Fig. 77. — Fucus vesiculosus. Fusiform and rod-shaped plastids (pi) with mito- 

 chondria im) and fucosan granules (p.p.) in Fucus vesiculosus. 1, apical cell; 2, two 

 celled embryo. N, nucleus. Regaud's method. (After Mangenot) . 



mosing to form a network, together with small chondriosomes. In 

 those portions of the thallus containing little chlorophyll (Fig. 

 78, Ii and lower portion of A), these elements grow thinner and 

 appear somewhat like chondrioconts. In the rhizoids (Fig. 78, I2), 

 in which neither chlorophyll nor phycoerythrin exists, the plastids 

 become very small and look so like the inactive chondriosomes that 

 it becomes impossible to tell them apart. The trichogyne and other 

 cells of the carpogonial branch (Fig. 78, A) develop from an 

 ordinary cell of the thallus containing large rhodoplasts. A regres- 

 sion of chlorophyll and of phycoerythrin may be observed in these 

 cells. The plastids lose their color and are transformed into small 

 rods becoming like the chondriosomes which are present with them 

 in the cell. Then the carpogonium shows a chondriome in which 

 all distinction between plastids and chondriosomes is impossible. 

 This chondriome persists in the first cells of the gominoblast fila- 



