13^ THE PLANT WORLD. 



closely so, while on feebly developed stems they are much more 

 loosely arranged. They are ovate in outline, but are remarkably 

 variable in regard to their lobes or teeth. On young or delicate stems 

 and branches, they are divided into two sharp lobes, separated by a 

 blunt sinus, which extends about one-third of the distance from the 

 apex toward the base. On robust stems the lobes are usually less 

 pronounced and blunt; sometimes, indeed, the leaves are simply 

 emarginate and sometimes, the sinus disappearing altogether, they 

 become truncate or obtuse at the apex. It is moreover common to 

 find all these variations on a single stem; but, except for the lobes, the 

 leaf -margins are quite entire. The leaf -cells do not vary greatly in 

 size in different parts of a leaf ; they are polygonal in outline and their 

 thin walls are not thickened at the angles. 



Underleaves are always present in this species and may be found 

 on the lower surface of the stem, one for each pair of leaves. It is, 

 however, sometimes difficult to see them on account of the rootlets. 

 They are small but distinct structures, and are divided almost to the 

 base into two lanceolate segments, which are either entire or bear a 

 small tooth-like protuberance on the outer margin at about the middle. 



In its inflorescence, LopJiocolea heteropJiylla is "monoicous," that 

 is the antheridia and archegonia are borne on the same plant; it is 

 furthermore of interest in the fact that these organs are developed 

 on the same stem, the archegonia being terminal and the perigonial 

 bracts being situated immediately beneath the perichaetial. If a stem 

 bearing a perianth is examined, the two or three pairs of perigonial 

 bracts may be at once recognized by the peculiar way in which they 

 embrace the stem. When they are dissected off and spread out, it 

 will be found that they are a little larger than the stem-leaves, but 

 are otherwise similar to them in shape and in variability. The under- 

 leaves corresponding to these bracts gradually increase in size toward 

 the perianth; they are less deeply cleft than those of the stem and 

 their marginal teeth sometimes attain a considerable size. The peri- 

 chaetial bracts, which are often reduced to a single pair, are longer 

 but narrower than the others, and are usually distinctly bilobed, the 

 lobes being variable and separated now by a broad, shallow sinus, 

 now by a narrow one. The bracteoles are quite free from the bracts, 

 and are similar in shape and size to the uppermost perigonial under- 

 leaf. The bracts and bracteoles often show on their margins a few 

 delicate and minute teeth, and the bracts sometimes bear close to the 

 base on the upper side one or more almost detached segments, which 

 are very variable in shape. There is, however, nothing answering to 

 the paraphyses of Jimgcrmaniiia barbata. 



The perianth of our Lophocolca is a very typical structure and 

 shows clearly the way in which this peculiar organ is built up. In 



