1907] CURRENT LITERATURE I51 
Purple bacteria——Motiscu describes two new genera of purple bacteria 
isolated in the laboratory from jars of sea water, sea grass, and decaying crabs 
or star-fish.37 For these forms he finds it necessary to add a new sub-family to 
WInocRADSKY’s and Micuta’s classification. This is sub-family VI. RHo- 
DOCAPSACEAE (cells free, not capable of swarming throughout life). Under 
this he places his two new forms, Rhodocapsa suspensa (cells sometimes capable 
of swarming, rods or threads with gelatinous capsule), and Rhodothece pen 
(power of swarming not as yet observed, cells round, with gelatinous capsule). 
—Mary HEFFERAN 
Origin of the pollen tube.—According to WeETTSTEIN,3* the rhizoidal tubes 
of the cycads and Ginkgo are to be regarded as completely homologous with the 
pollen tubes of the higher gyninosperms and the angiosperms. The writer then 
attempts to show that the rhizoidal tube of the cycads and Ginkgo is homologous 
with the vegetative end cell of the heterosporous pteridophytes. The rudimen- 
tary or rhizoidal cell of the heterosporous pteridophytes does not lead to the 
rhizoidal tube of the cycads and Ginkgo, and is still represented in these lower 
gymnosperms by a prothallial cell. Chalazogamy is regarded not as a primitive 
condition, but merely as an interesting special case. The paper is a preliminary 
statement without figures.—CHARLES J. CHAMBERLAIN. 
37 Moriscu, Hans, Zwei neue Purpurbakterien mit Schwebekérperchen. Bot. 
Zeit. 64:223-232. pl. 8. 1906. 
38 WETTSTEIN, R. von, Der Ursprung des Pollenschlauches. Naturw. Rundschau 
2121-2. 1906. 
