I 



NOTES AND MEMORANDA. 305 



Martin Lister, two hundred years ago, noted the production of fila- 

 ments 2 feet long; Shaw, in 1776, observed filaments 8 feet from the 

 groimd, and Hoy, in 1789, gave an account of them to the Linnaean 

 Society. For many years these and similar observations seem to have 

 been well known, but since the time of Woodward, Johnston, and 

 Moquin-Tandon, no information is given in the more popular manuals. 

 Professor Martens notes as a curious fact that the majority of obser- 

 vations on the habits of Limax has been made in Great Britain, anp, 

 though making full allowance for the superior advantages of our 

 damp climate, thinks that the fact is due to the better instruction and 

 greater interest of our naturalists. He observes, that the power of 

 producing these threads is not confined to Limax, but that Megalo- 

 mastoma suspensum in the West Lidies, and Potamides obtosus on the 

 coasts of Borneo, have been observed to have it also ; and, noting the 

 striking resemblance between these, and the byssus-threads, concludes 

 by observing that there are marine Gasteropoda capable of producing 

 similar filaments. 



BOTANY. 



A. GENERAL, INCLUDING EMBRYOLOGY AND 

 HISTOLOGY OE THE PHANEROGAMIA. 



Development of the Embryonal Sac. — The following are the 

 summarized results of M. J. Vesque's researches on this subject.* 



1st. In Angiosperms, the embryonal sac of Brougniart is not 

 composed, as in Gymnosperms, of a single cell; on the contrary, 

 it results from the fusion of at least two cells superposed and at first 

 separated by septa. 



2nd. The cells which are destined later on to compose the em- 

 bryonal sac, all proceed from one and the same primordial parent- 

 cell. M. Warming, who discovered them, rightly gives them the 

 name of special parent-cells, comparing them to the parent-cells of 

 pollen or of spores. This comparison is justified by the physical 

 characters of the septa. 



3rd. When the development of the special parent-cells is com- 

 pleted, each gives rise to four vesicles homologous to the four pollen 

 grains which originate in one and the same parent-cell. 



4th. The variations to be observed in the different types of 

 Angiosperms depend on the more or less early arrest of development 

 which happens to the special parent-cells. 



5th. The first cell always produces the sexual apparatus. It 

 blends with the second cell, in order to constitute the major part of 

 the embryonal sac. When the second cell has produced its four 

 vesicles, the eight free vesicles of the embryonal sac behave in the 

 manner described by Strasburger in the cases of Orchis and 

 Monotropa. This fact is observed in certain Monocotyledons and 

 apopetalous Dicotyledons. 



6th. The other special parent-cells (the third, fourth, and fifth) 



may produce the four vesicles. Each of the vesicles is homologous 



with the pollen grain, and it is convenient to retain for it the name 



of antipodal vesicle. When these parent-cells persist in their primi- 



* ' Ann. des Sci. Nat. (Bot).," xi. (1878) 27G. 



VOL. II. X 



