480 Mr. Valentine on the Development of the Theca, 



good reason for supposing that the vivifying matter communicated by the 

 pollen tubes to the placenta is by some unknown means transmitted by the 

 latter to the foramen of the ovulum, through which it finally passes into the 

 nucleus, there to become the new embryo*." It is a well established fact that 

 the embryo, or essential part of the seed, is derived from the pollen, and that 

 the membranes which are produced by the pistillum only act as a protection 

 and channel of nutrition to the embryo, until such time as it shall be enabled 

 to provide for itself. Mr. Drumraond, in a paper published in the 13th volume 

 of the Linnean Transactions, proved, beyond a doubt, that the sporules of 

 Mosses germinate by emitting " pellucid filaments" from any points in their 

 surface. I have myself examined the germinating sporules of Funaria hygro- 

 metrica ; and I found that the brown coat burst sometimes in two or three 

 places, but most frequently in one only ; and there protruded from each fissure 

 a delicate transparent tube containing the moving particles, which had pre- 

 viously occupied the cavity of the sporule. These tubes, or, to speak with 

 more precision, elongated cells, gradually increased in length, and, from 

 exposure to light, became of a green colour. They soon became jointed, from 

 the addition of fresh cells at the extremities. They then began to branch, and 

 after a time produced leaves. 



The only difference that I can find between pollen and sporules is, that 

 the coat of the latter is of a more rigid and opake texture. From this 

 difference it is that the sporules rarely burst in a sudden manner upon 

 the application of water ; but when they do, the moving particles are dis- 

 charged loose in the water, precisely in the same manner as are those of the 

 pollen. In both sporules and pollen it is necessary, to the production of the 

 tubes, that the laceration of the coats should take place slowly. 



Without reference to the evidence here adduced, we do not overstep the 

 bounds of probability in supposing that in plants of a complicated organiza- 

 tion there exists a necessity that the embryo should be protected by a nidus 

 capable of imparting aliment until it shall become sufficiently organized to be 

 capable of reproducing a plant equal in complexity of structure to its parent. 

 Whilst in the Cellulares the process of their growth is so little complicated 



* Mr. Brown has actually traced the pollen tubes into the foramen of the ovulum in Orchis Morio, 

 Habenaria viridis and Ophrys apiferu. See Linnean Transactions, vol. xvi. p. 742. 



