518 



HUTCHINSON'S POPULAR BOTANY 



ground as far south, as Cornwall and Sussex. It has been likened to a 

 fir-tree in miniature, but it might easily be mistaken for an early 

 condition of a coniferous seedling. It has little of the clubbed character, 

 and it does not creep. All its shoots take an upward direction, and it 

 therefore forms bushy clumps. In common with those of several other 

 species, some of the lower leaves of the cone produce buds instead of 

 sporanges, and these separate and fall to the ground, where they develop 



directly into plants without the interven- 

 tion of the prothallium stage. 



The Order Selaginellacese consists of 

 the two genera Selaginella and Isoetes, both 

 of which are represented by British species. 

 Both megaspores and microspores are pro- 

 duced, but in a manner different from those 

 of the Water-ferns, and the prothallium is 

 quite devoid of chlorophyll. Our only 

 native species of Selaginella is the Lesser 

 Alpine Club Moss (Selaginella selaginoides), 

 a small moss-like plant inhabiting bogs and 

 marshes. Several of the numerous exotic 

 species are well known in our conserva- 

 tories and greenhouses. S. selaginoides has 

 creeping stems only a few inches long and 

 completely clothed all round with overlap- 

 ping lance-shaped leaves. A few branches 

 are of more erect growth, and the leaves of 

 these are longer, more closely pressed to 

 the stem, which ends in a stouter scaly 

 cone about an inch long. This cone is 

 the part of the plant that bears the spor- 

 angia, and the leaf-like scales containing 

 them are known as sporophylls. The spor- 

 ange, on a short stalk, springs from the 

 stem just above the base of the sporo- 

 phyll. Those in the lower sporophylls are 

 spherical and megasporanges ; in the 

 upper sporophylls, there are flattened micro- 



sporanges (fig. 659). Each megasporange contains only three or four 

 megaspores, which are set free by the splitting of the sporange into 

 three or four valves; the microsporanges are only two-valved, and their 

 contents are minute and numerous. Both kinds of spores are invested by 

 three coats endospore, exospore, and epispore. The growth of the pro- 

 thallium within the apical portion of the megaspore proceeds pari passu 

 with the development of the larger body, whilst the protoplasm which 



FIG. 



1. QTJILLWOBT (Isoetes 

 lacustris). 



(a) Leaf with sporange in base, (b) Base of leaf 



on larger scale, (c) Transverse section through 



ripe sporange, showing spores. 



