452 Messrs Gardiner and Hill, The Histology 



accomplished, the cotyledons are withdrawn from the depleted 

 seed and unfold in the air, where they perform the functions of 

 the ordinary green leaves 1 . 



In making a comparison between Tamus communis and 

 Galium Tricorne it is interesting to note the great difference 

 between the behaviour of the two seeds during germination. The 

 composition of the cell walls appears also to be different in the 

 two cases. In Galium, judging from microchemical reactions, it 

 approaches more nearly to a pecto-cellulose, but in Tamus the 

 walls appear to be composed of the so-called "reserve-cellulose," 

 very similar to that described by Gruss 2 in the endosperm of 

 Phoenix sylvestris. 



It is not unlikely that the character of the enzyme action 

 during the germination of these two seeds has some relation to the 

 differences in the composition of their cell walls. 



In the case of Tamus the mode of attack of the enzyme, which 

 apparently is secreted by the cotyledon, is, with reference to the 

 embryo, centrifugal, whilst in Galium, on the other hand, it is 

 centripetal ; in this latter case it is the cells of the endosperm 

 Avhich appear to contain the enzyme, or perhaps rather a zymogen 

 which gives rise to an enzyme. It is possible that the formation 

 of the enzyme or zymogen may be determined by a stimulus 

 chemical or otherwise proceeding from the embryo. 



On germination of the seeds the enzyme is liberated in the 

 cells and commences to attack the walls and work towards the 

 embryo in a centripetal manner. In both cases it was noticed 

 that although in the first instance the walls were frequently 

 entered by a ferment along the course of a thread, their subsequent 

 disorganization took place without any definite relation to the con- 

 necting threads in the cell wall. 



Strasburger 3 , who has recently examined the endosperm of 

 Tamus in connection with his work on "connecting threads," 

 forms a somewhat different conclusion. He confirms the results 

 which had been previously obtained 4 , but he considers that the 

 chief function of the threads is to serve as the passage ways by 

 which the enzymes enter and travel through the walls and effect 

 their solution during germination. Further, he attempts to prove 

 that it is the threads which traverse the thickness of the wall (the 

 " solitary threads " of Kohl 5 ) rather than those found in the pit- 



3 Cf. Lubbock, loc. cit. 



2 Gruss, "Studien riber Eeserve-cellulose," Bot. Cent., 70, 1897, p. 242. 



3 Strasburger, " Ueber Plasmaverbindungen pflanzlichen Zellen," Jahr. f. Wiss. 

 Bot., Bd. xxxvi. Heft 3, pp. 535 — 538. 



4 Gardiner, Proc. Roy. Soc. 1897. 



5 Kobl, Ber. d. Deut. Bot. Ges. 1900. Dimorphic threads had been previously 

 described in the paper in the Phil. Trans. Roy. Soc. 1883, in the endosperm of 

 Bentinckia, Howea, Lodoicea and Phytelephas, with figures. Cf. also Gardiner, 

 Proc. Roy. Soc. 1897, p. 104. 



