NOVEMBEB 13, 1908] 



SCIENCE 



691 



the spectra this morning, but have no doubt that 

 they will prove to show the ordinary hydrocarbon 

 spectrum. 



The photographs taken last night at the 

 Harvard Observatory show a tail at least nine 

 degrees in length, and much longer than on 

 previous nights. 



Edward C. Pickering 



HABVAED COIiEGE Obsebvatobt, 

 October 31, 1908 



SPECIAL ARTICLES 



note on the occurrence of rhodochytkium 

 spilanthidis lagerheim in north 



AMERICA 



In the Botanical Gazette for October, 1908,' 

 there is published a note on the occurrence of 

 this interesting parasite upon the leaves of 

 the ragweed (Ambrosia art emisice folia) in 

 North Carolina, This short note is published 

 in the hope that some readers who do not 

 have access to the Gazette may have their at- 

 tention called to this organism and that they 

 may be on the lookout for it in other sections. 



The plant is an alga devoid of chlorophyll. 

 It is parasitic on the leaves, stems, pedicels, 

 flower bracts, etc. It begins its development 

 in early summer on the small seedlings and by 

 developing succeeding crops of zoospores con- 

 tinues infection of these same plants through- 

 out the season, until finally the flower racemes 

 are affected. The main body of the parasite 

 forms sporangia which vary from 50 to 300 fx, 

 in diameter, the smaller ones being on the 

 leaves. The plant has a reddish-yellow oil 

 deposited in the protoplasm which is so massed 

 in the larger sporangia that it causes a bright 

 red color visible through the thin layer of 

 cortical tissue, so that the plant has the ap- 

 pearance of being studded with minute red 

 dots, suggesting a Synchytrium. The plant 

 is always located in or adjacent to the vascular 

 bundles. There is an extensive system of 

 mycelial rhizoids which are profusely 

 branched. These rhizoids extend both up and 

 down. The terminal mycelium is provided 



" Atkinson, G. F., " A Parasitic Alga, Rhodo- 

 chytrium spilanthidis Lagerheim, in North Amer- 

 ica," Bot. Oaz., 46, 299-301, 1908. 



with numerous haustoria, many of which are 

 often applied very closely to the spiral ducts, 

 but never entering them, so far as I have ob- 

 served. The plant body remains connected with 

 the outside wall by the entrance tube. The 

 outer end of these tubes is broadened into a 

 trumpet-like expansion which is the remains 

 of the zoospore wall. The plant thus re- 

 sembles a giant Entophlyctis. The outer end 

 develops into a broad exit tube through which 

 the zoospores escape. The zoospores are bi- 

 ciliated, containing a reddish-yellow oil which 

 is accumulated in the forward end of the 

 elliptical zoospore where the two cilia are 

 attached. Many of the zoospores conjugate 

 in pairs, this taking place during the process 

 of swimming. When the zoospores come to 

 rest, they become rounded and are 8-10 ;u, in 

 diameter. The zygozoospores are considerably 

 larger. 



The resting spores are provided with a very 

 thick wall which is divided into three layers. 

 At maturity there is an abundance of the 

 reddish-yellow oil in the resting spores which 

 is withdrawn along with the protoplasm and 

 starch from the rhizoid system. The rhizoids 

 then become plugged where they join the main 

 body of the sporangium. The inner wall of 

 the resting spores is laid down entirely dis- 

 tinct from the other walls and forms a com- 

 plete envelop around the content which can be 

 separated distinctly as the endospore from the 

 other walls. The sporangia as well as the 

 rhizoids are provided with starcL Great 

 masses of starch are present in the sporangia. 

 This starch is not, however, manufactured 

 through the photosynthetic process by the 

 organism, but is obtained from the host. 



This organism, Bhodochytrium spilanthidis 

 Lagerheim^ was described by Lagerheim' 

 fifteen years ago, from material collected on 

 a species of Spilanthes in Ecuador. Though 

 Lagerheim searched diligently on other genera 

 he found it occurred only on Spilanthes. 

 Here is then an interesting problem of dis- 

 tribution. Collectors in the southern part of 



'Lagerheim, G. de, " Rhodoohytrium, nov. gen., 

 eine Uebergangsform von den Protocoecaceen zu 

 den Chytridiaceen," Bot. Zeit., 51, 43-53, pi. 2, 

 1893. 



