260 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Struvea.* — Messrs. G. Murray and L. A. Boodle give a monograph 

 of this genus of Siphonocladacese, of which they make five species : — 

 S. plumosa Sond., S. macrophylla Harv., ;S^. ramosa Dick., S. delicatula 

 Kiitz., and S. pulcherrima nob. (Pliyllodictyon pulcherrimum Gray), 

 excluding S. scoparia Kiitz,, which appears to be identical with Apjohnia 

 Isetevirens Harv. 



The organs described are the stalk, the root, and the frond. The 

 stalk consists of a single cell from its earliest stages to the time of 

 formation of the frond, when a transverse wall is formed a short distance 

 below the base of the frond. The calcareous incrustation described by 

 some authors is due to the presence of an epiphytic calcareous alga, 

 generally a Melohesia. In S. ramosa the pinnae of the frond consist of a 

 series of segments separated by transverse walls. The pinnas are again 

 divided into pinnules. When a pinnule has, in its growth, brought its 

 tip into contact with another part of the frond, it forms at its apex a 

 special organ of attachment, called by the authors a tenaculum, con- 

 sisting of a ring of radiating branched rhizoids, which, however, appear 

 to be entirely superficial, never penetrating the cell-wall to which they 

 are attached. Similar organs occur in other species, as well as in some 

 allied genera. Although filaments become attached to one another by 

 means of these tenacula, there is no true anastomosis, as described by 

 Harvey and Dickie. 



No reproductive organs were detected in any species of Struvea ; but 

 in S. ramosa, singular structures at the base of some of the filaments of 

 the frond, resembling in shape the sporanges of Botrydium. Until the 

 organs of reproduction are known the position of the genus is somewhat 

 uncertain ; but it appears to connect Valonia on the one hand with 

 Cladophora and Spongocladia on the other hand. 



Sexuality among the Lower Algse.t — M. P. A. Dangeard believes 

 that a sexual mode of reproduction will eventually be found to occur in 

 many of the lower algge where it is at present unknown, and that it is in 

 particular incited by defective nutrition, progressive desiccation, the 

 action of injurious substances, and other similar causes. 



He describes its occurrence in Phacotus angulosiis, an organism first 

 described by Carter under the name Cryptoglena angulosa, and usually 

 placed among the Protozoa. Under cultivation the non-sexual mode of 

 propagation was found to be almost suppressed. On the other hand 

 individuals, after losing their cilia, formed four or eight small biciliated 

 zoogametes by successive bipartitions. These swarmed for a time within 

 the parent-cell, then escaped, and finally conjugated with very great 

 rapidity, losing their cilia, into a spherical oosperm. These zoogametes 

 differed from all others previously observed in having the chlorophyll 

 located at the anterior extremity. The author believes that the bodies 

 previously described as resting-cells in this genus are in reality 

 oosperms. No sexual differentiation was observed in the zoogametes. 

 Phacotus forms, therefore, sexually produced oosperms in the same way 

 as Chlorogomum,\ Cercidium, and Chlamydomonas ; and these genera 

 must be regarded as belonging to the same family. 



A new marine species of Chlamydomonas is described, C. minima. 



* Ann. of Bot., ii. (1888) pp. 265-82 (1 pi.). 



t Morot's Journ. do Bot., ii. (1888) pp. 350-3, 415-7 (2 figs ). 



t See tliis Journal, 1888, p. 1003. 



