Back to Top Causes. Toxic megacolon occurs as a complication of inflammatory bowel disease, such as ulcerative colitis and Crohnâs disease, and infections of the colon. The term toxic means that this complication occurs with infection or inflammation and is very dangerous.This is not the same as other forms of megacolon, such as pseudo-obstruction, acute colonic ileus, or congenital colonic dilation. These conditions occur without infection or inflammation.he term toxic means that this complication occurs with infection or inflammation and is very dangerous. This is not the same as other forms of megacolon, such as pseudo-obstruction, acute colonic ileus, or congenital colonic dilation. These conditions occur without infection or inflammation.
Leaf: The green, photosynthetic part of the plant is technically a megaphyll and in ferns, it is often referred to as a frond. New leaves typically expand by the unrolling of a tight spiral called a crozier or fiddlehead fern. This uncurling of the leaf is termed circinate vernation.
Ferns are vascular plants differing from lycophytes by having true leaves (megaphylls), which are often pinnate. They differ from seed plants (gymnosperms and angiosperms) in their mode of reproductionâlacking flowers and seeds.he gametophytes of ferns, however, are very different from those of seed plants. Instead, they resemble liverworts. A fern gametophyte typically consists of: 1  Prothallus: A green, photosynthetic structure that is one cell thick, usually heart or kidney shaped, 3â10 mm long and 2â8 mm broad.