454 Messrs Gardiner and Hill, The Histology 



certain that this function of the connecting threads in ripe endo- 

 sperm tissue must be one of only a secondary character. 



We consider, moreover, that there is at the present time, and, 

 in the light of existing researches, insufficient ground for laying 

 stress on the differences between the pit and wall threads or of 

 assigning to either of them any special or distinctive function 

 although it is not improbable that some such distinction does 

 as a matter of fact exist. 



As to the principle or master function of the connecting threads 

 in the endosperm, there can be little doubt that the opinion already 

 set forth 1 , and to which Strasburger 2 takes exception, is the true 

 view of the case, namely, that the " connecting threads " are 

 primarily essential for the conduction of food and stimuli during 

 the development of the endosperm and the seed, and that in such 

 seeds as those of Tamus and Galium the period during which their 

 functions are discharged with greatest perfection is " inter vitam " 

 and not "post mortem." Endosperms such as that of Phoenix 

 rupicola which possess the two forms of threads lend additional 

 support to this conclusion, since the wall threads are found in large 

 numbers at those parts where they would naturally be most useful, 

 for they occur not only in the walls of the peripheral endosperm 

 tissue, where they would serve as channels of communication 

 between the developing seed and the parent plant, but also in the 

 walls of the cells which immediately surround the embryo itself. 



The conclusions to which we are led by a study of the germina- 

 tion of the seeds of Tamus and Galium are that although the 

 ferments can attack and dissolve the thick cell walls of the endo- 

 sperm, without any necessary relation to the "connecting threads," 

 yet that in the initial stages the penetration of the enzyme may be 

 effected by means of the threads, which thus afford a means of 

 reaching the internal parts of the wall. 



Secondly, that the connecting threads are concerned mainly 

 and primarily with the conduction of food and stimuli from the 

 parent plant to the developing embryo and endosperm of the seed, 

 and that any further use to which they may be put during the 

 germination of the seed must be regarded as only of secondary 

 significance. 



1 Gardiner, Proc. Roy. Soc. 1897, p. 107. 



2 Strasburger, loc. tit., p. 536. 



