488 Mr. Valentine on the Structure and Development 



sixteen in number, and in the leaf (Tab. XXXV. fig, 24.) and root they are 

 about ten or twelve ; in the latter they are arranged in pairs (Tab. XXXV. 

 fig. 25.). These partitions radiate from a central column of enlarged cells 

 which surround a bundle of minutely dotted ducts, that may be unrolled spi- 

 rally (Tab. XXXV. fig. 27.), and the channels between these partitions are 

 frequently divided by transverse partitions or diaphragms. The cells which 

 form these partitions are curiously arranged (Tab. XXXV. fig. 27 &28.) ; they 

 are flattened on two opposite sides, and connected with each other by their 

 narrow sides and extremities, but only at intervals, so that there are numerous 

 holes formed which afford a free communication between all the channels. In 

 the partitions of the root, the intervening holes are so large in proportion to 

 the breadth of the cells, that these have the appearance of a string of beads 

 (Tab. XXXV. fig. 28.). Another peculiarity of the root is, that, in addition 

 to the diaphragms formed of this tissue, which are also found in the stem and 

 leaf, a peculiar body is frequently met with, occupying a similar position to 

 the diaphragms (Tab. XXXV. fig. 25.). These bodies (for they are sometimes 

 numerous) are each formed of one or more cylindrical cells coiled up in a 

 gyrate manner. They grow from the angle formed by the partition and the 

 cuticle, and are developed subsequent to the other tissue, for they may be 

 found in various stages of advancement in the same root. Their nature I have 

 not been able to ascertain. 



I shall now proceed to describe the development of the sporules. A trans- 

 verse section of the involucrum, when about the size of a small pin's head, 

 shows it to consist of four integuments containing a mass of very delicate, 

 spongy, compressible cellular tissue, subdivided into four equal triangular por- 

 tions by four lines radiating from the centre. In the centre of each of these 

 portions is a cavity, and projecting into each of these cavities are a number of 

 nipple-like processes, which are attached in each cavity to a common recep- 

 tacle, whilst this, again, is connected with an open, rigid, cellular tissue, that 

 lies between the spongy tissue, before described, and the involucrum, and serves 

 as a connexion between the two (Tab. XXXV. fig. 29.). As the involucrum 

 advances, the spongy tissue recedes all round the four cavities, which con- 

 sequently become larger, and afford more space for the growth of the nipple- 

 like processes. This recession of the spongy tissue is not caused by the pressure 



