1891.] Morphology of Spore-producing Members. 267 



The sporophyte consists of two parts : (i) the protocorm, with its 

 protophylls and roots, and (ii) the strobilus, with sporophylls and 

 sporangia. The transition from (i) to (ii) is usually sudden, and 

 without intermediate steps. 



The sporangium of Phylloglossum, as regards its external form, is inter- 

 mediate in character between that of Lycopodium Selago andi. alpinum; 

 the archesporium consists of a single row of about six cells, only one 

 of which appears in each radial section ; in this, Phylloglossum is like 

 L. selago. The whole strobilus also, when mature, is closely similar 

 to that of a simple Lycopodium, and the development of the spor- 

 angium corresponds also in all essential points. 



Several species of Lycopodium have been examined as regards the 

 structure and development of the sporangium ; previous investigators 

 have figured only radial sections ; it is obvious that radial, transverse, 

 and tangential sections in various stages will be necessary for the 

 complete description of the development of so large and complex a 

 body ; the result of comparison of such sections has been (i) to acquire 

 a clear knowledge of the form and composition of the arche- 

 sporium, and (ii) to show that this varies in different species of the 

 genus. 



Two cases will be briefly described, viz., L. Selago and.L. clavatum. 



In the former the sporangium appears as a rather narrow, sharply 

 convex outgrowth from the upper surface of the sporophyll ; the 

 archesporium consists of a single row of cells, of which one only 

 appears in the radial section ; the smallest number seen in the tan- 

 gential sections is seven, which may possibly be referable in origin 

 to three parent cells. While the archesporium increases largely with 

 age, neither the stalk of the sporangium nor the sub-archesporial tissue 

 increases greatly in bulk, so that the mature sporangium assumes the 

 form of a slightly curved sausage, attached by a comparatively slender 

 and long stalk. 



In L. clavatum (to which also L. alpinum closely corresponds), 

 the sporanginm appears as a broad, only slightly convex out-growth ; 

 the archesporium does not consist of a single row of cells, but usually 

 of three rows : thus three cells would appear in each radial section : 

 both radial and transverse sections show that these are not readily 

 referable in origin to a single parent cell. In tangential section it 

 appears that ten or more cells may be present in each row. As the 

 archesporium grows, the stalk remains short and bulky, while the 

 sub-archesporial mass develops as a large pad of sterile tissue, which 

 arches the sporogenous tissue convexly upwards. The whole spor- 

 angium when mature is thus strongly curved, and is inserted on the 

 sporophyll by a short and massive stalk. These characters, are im- 

 portant for comparison with Ophioglossum. 



It may be added that, so far as observations have yet been made on 



