212 Cklorococcinese 



of the host-plant after the manner of Phyttosiphon among the Siphonales, 

 and often becoming septate. Projecting from the surface of the leaf are 

 numerous swellings of a bright green colour, which are resting akinetes. 

 These are upwards of twenty times the diameter of the branched tubes from 

 which they arise, and the chloroplast is a thin parietal layer from which 

 numerous rod-shaped lobes (most of which possess a pyrenoid) radiate into 

 the central cavity. Reproduction occurs in this genus by zoogonidia and 

 also by anisogametes (fig. 137 C b e), the zygote developing at once into a 

 young Phyllobium-plant (fig. 137 Of and g\ 



The so-called ' genera ' Endosphaera, Scotinosphsera, Chlorocystis and Stomatochytrium, 

 should all lie submerged in Chlorochytrium, as they are discriminated from each other and 

 from that genus by the most trivial characters, not one of which can be regarded as of 

 generic importance. In Chlorochytrium reproduction by both zoogonidia and gametes has 

 been repeatedly shown to occur. Scotinosphasra (Klebs, '81) is identical in all respects with 

 Chlorochytrium^ except that reproduction is said to occur in the former by isogametes only 

 and in the latter by zoogonidia only. Such distinctions are of no taxonomic value among 

 lower forms of Green Algae, and the separation of so-called 'genera' on such characters 

 cannot be upheld. Chlorocystis is merely a Chlorochytrium in which the chloroplast is a 

 little more restricted and contains only one pyrenoid. In Endosphs&ra the resting-cells 

 form numerous gametangia (vide fig. 137 B a) each of which produces 8 16 biciliated 

 gametes which fuse in pairs, the quadriciliated ' zygozoospores ' entering the intercellular 

 spaces of the host. 



All the more recent work on this group of Alga; has .shown that Cohn and other 

 previous investigators were wrong in regarding certain forms as parasites, and that not 

 merely can the endophyte live quite independently of its host-plant, but that in most cases 

 the latter receives no injury beyond that which may be caused by the little mechanical 

 pressure exerted by the growing endophyte. Freeman ('99) has suggested that the general 

 biological conditions under which Chlorochytrium lives lend themselves to the development 

 of parasitism, and that the allied genus Phyllobium is progressing in that direction 1 . 

 Chlorochytrium ( = Chlorocystis) Sarcophyci is the cause of deformities in the thallus of the 

 seaweed Sarcophycus (Whitting, '93). 



The genera are : Chlorococcum Fries, 1825 \_-Cystococeus Nageli, 1849]; Chlorochytrium 

 Cohn, 1874 [inclus. Endosphsera Klebs, 1881 ; Scotinospheera Klebs, 1881 ; Chlorocystis 

 Reinhard, 1885 ; and Stomatochytrium Cunningham, 1888] ; Phyllobium Klebs, 1881 ; 

 Centrosph&ra Borzi, 1883 ; ? Dictyococcus Gerneck, 1907. 



Sub-family DICRANOCH.ETE^E. This sub-family includes only the single 

 genus Dicranoch&te Hieronymus (1892), which differs from all the other 

 members of the Planosporacea? in the possession of bristles. The latter are 

 also of a unique character, being dichotomously branched ; bristles of such a 

 nature are entirely unknown in any other group of Algse (consult fig. 139). 

 The cells are solitary and attached to the leaves of submerged species of 

 Sphagnum and Hypnum ; they are uninucleate and possess a single massive 

 chloroplast with or without pyrenoids. In D. reniformis Hieronymus ('92) 



1 The Archimycetes (Chytridiea?) show many striking resemblances to Chlorochytrium. 



