1 9 i4l JEFFREY— SPORE CONDITIONS 325 



Sphagnum. As is well known, this genus is extremely variable, 

 and the species are often difficult to distinguish. It appears accord- 

 ingly not improbable that the abortion of spores sometimes found 

 here may be correlated with hybridism in nature. Fig. 2 shows 

 the homogeneous character of the spores in the common species 

 Polytrichum commune. As is the case in the leafy mosses or 

 Phyllobrya in general, there are no elaters present. 



Numerous representatives of the Lycopodiales, heterosporous 

 and homosporous, were examined and abortive spores were seen 

 to be characteristically absent. Five species of Lycopodium, as 

 well as Phylloglossum, Psilotum, Tmesipteris, Selaginella, Isoetes, 

 Lepidodendron, Spencerites, etc., all yielded uniform results. 



One species of Equisetum has long been recognized to be of 

 hybrid origin, namely E. littorale, which from its anatomical and 

 external features is a hybrid between E. arvense and E. limosum. 

 It is one of the few conventionally recognized hybrid species, and 

 is characterized by the large number of abortive spores which are 

 found in its sporangia. Miss Holden has recently published in 

 Science an interesting account of abortive sporogeny, accompanied 

 by blended anatomical features, in Equisetum variegatum var. 

 Jesupi. It appears beyond question, from Miss Holden's work, 

 that this variety is the result of a cross between E. hiemale and 



■ 



E. variegatum. .It is further probable from her work that other 

 recognized varieties of species of Equisetum are likewise hybrids 

 in their origin. Fig. 3 represents a section through part of a spo- 

 rangium in E. hiemale. Although all of the spores are not equally 

 in the plane of section, it is clear that they are normal and un- 

 mingled with abortive individuals. In fig. 4 is shown a view of a 

 section through a sporangium of E. variegatum var. Jesupi. Here 

 there are practically no sound spores, unless one to the right of the 

 figure can be considered sound. Even the spores of relatively large 

 size and dark (protoplasmic) contents are abnormal. The smaller 

 and abortive spores, which enormously predominate in the figure, 

 have very scanty protoplasmic contents or none at all. Contrary 

 to statements usually made in regard to abortive spores of 

 Equisetum, the elaters are present, although not normally devel- 

 oped- They can be seen as circles bounding the spore proper 



