TILICINEM. 



479 



sporangia, the inner ones only microsporangia, the former containing a large number 

 of macrospores. Both kinds of sporangia are imperfectly chambered by bands of 

 tissue {trabeculcB) which cross from the ventral to the dorsal side. The sporangia do 

 not dehisce, but the spores escape by the decay of the wall. 



In the SelaginellecB the sporangia are shortly stalked roundish capsules. The 

 macrosporangia contain usually four, less often two or eight macrospores. In the 

 division of Articulatae the lowermost sporangium only of a spike produces macro- 

 spores ; in the other divisions there are several macrosporangia. The sporangia do 

 not take origin, as Hofmeister's older accounts would seem to show, from single cells 



Fig. 337.— Development of the sporangia and spores of Selaginella inaqualifolia ; the order of succession is indicated 

 by the letters A—D; A and B serve for all the sporangia, C and D for the microsporangia only ; E division of the mother- 

 cells of the microspores, h four nearly ripe spores ; in ^, C and D, a, b are the two layers of the wall of the sporangium, 

 c is the tapetum, d the primary mother-cells of the spores (A, B and £ X Soo ; C and D X 200). 



of the epidermis, but, as in Lycopodium^ from a group of such cells (according to 

 GoebeP). 



The sporangia arise on the growing-point of the stem immediately above 

 the base of the corresponding leaves, but this by no means justifies us in regarding 

 them as cauline organs as Russow does. Like those of Lycopodium^ they at first 

 appear as flattened protuberances which become more or less spheroidal at a later 

 period and finally clavate. At a later period the sporangia appear to be inserted 

 in the axil of the leaves or on their base. The fibro- vascular bundle of the leaf runs 



[Beit. z. Vergl. Entwick. d. Sporangien; Pot. Zeitg. 1881.] 



I. 



