36 AGRICULTURE OF MAINE. 



body, technically known as a perithecium, and he finds thai 

 there is a definite correlation between the development of these 

 bodies and the pushing forth of buds on the apple tree in the 

 spring. At about the time the blossom buds are unfolding, at 

 least by the time of opening of the blossoms, it is found that 

 the perithecium has become fully matured. Upon examining 

 into the structure of one of these bodies with the microscope, 

 it is found that it is essentially composed of a thick, black pro- 

 tective covering, on the interior of which there are numerous 

 tubular sacs, each of which contains eight oblong, brown spores 

 or reproductive bodies. If the perithecium is carefully pricked 

 out of the leaf tissue and placed in a drop of water for exami- 

 nation with the microscope, it will be observed, if the spores 

 are matured, that the tubular sacs absorbing the water become 

 very much lengthened and protrude from the apex of the 

 perithecium through a minute opening which does not appear 

 until the perithecium makes its last increase in size. The spores 

 enclosed in the sacs are crowded to the apex and spore after 

 spore is violently ejected, all eight spores being discharged 

 within a minute or two. When all of the eight spores have 

 been ejected the empty sac collapses and its place is taken by 

 another and thus the process repeated. As a single perithecium 

 may contain two hundred such sacs, one can readily calculate 

 how many spores might be cast from a single one of these 

 bodies. Leaves are often found on which the perithecia are 

 exceedingly abundant and in one case, in an examination by us, 

 it was found that if there were a continuous layer of leaves 

 under a tree spreading 40 feet, bearing perithecia in the abun- 

 dance of the fragment under examination, there might be 

 ejected during a period of 45 minutes of rainy weather not 

 less than eight billion spores. 



While it has just been stated that these spores are ejected 

 with violence, the height into the air to which they are ejected 

 is not more than one-fourth of an inch. The exceedingly small 

 size of these spores, however, permits them to float about in the 

 air more readily than particles of dust, and the impulse afforded 

 by the mechanical ejection from the sac is sufficient to place 

 them in air currents which may carry them to apple foliage. Tt 

 is obvious that the greater majority of spores lodge in un- 



