336 MICROSCOPIC STRUCTURE OF HIGHER CRTPTOGAMIA. 





Surcina ventriculL 



considerable amount without producing any inconvenience ; 

 it seems probable, therefore, that its presence in disease is 



rather to be considered as fa- 

 FiG. 119. vored by the changed state of 



the fluids which the disease 

 induces (either an acid or a 

 fermentable state of the con- 

 tents of the stomach having 

 been generally found to exist 

 in the cases in which the plant 

 has been most abundant), than 

 to be itself the occasion of the 

 disease, as some have supposed. 

 The Sareina presents itself in 

 the form of clusters of adhe- 

 rent cells arranged in squares, 

 each square containing from 

 4 to 64, and the number of cells being obviously multiplied 

 by duplicative subdivision in directions transverse to each 

 other. In fact, its general mode of growth would indicate 

 a near relationship to Q-onium, one of the Volvocinese, which 

 presents itself in similar quadripartite aggregations ; and many 

 Botanists, looking to this circumstance, and to the residence 

 of the plant in liquid, regard it as belonging to the group 

 of Algse. It agrees with the Fungi, however, in not living 

 elsewhere than in liquids containing organic matter ; and there 

 can be little doubt that, as no fructification has yet been seen 

 in it, only its earlier and simpler condition is yet known to 

 us. Its true place cannot be determined, until its whole life- 

 history shall have been followed out. There is a form of 

 Fungous vegetation that is prone to develope itself within the 

 living body, which is of great economic importance, as well as 

 of scientific interest ; this is the Botrytis bassiana (Fig. 120), a 

 kind of "mould," the growth of which is the real source of a 

 disease termed Museardine, that sometimes carries ofi" Silk-worms 

 in large numbers, just when they are about to enter the chrysalis 

 state, to the great injury of their breeders. The sporules of this 

 fungus, floating in the air, enter the breathing-pores which open 

 into the tracheal system of the silk- worm (Chap. XVII) ; they first 

 develope themselves within the air-tubes, which are soon blocked 

 up by their growth ; and they then extend themselves through 

 the fatty mass beneath the skin, occasioning the destruction of 

 this tissue, which is very important as a reservoir of nutriment 

 to the animal, when it is about to pass into a state of complete 

 inactivity. The disease invariably occasions the death of the 

 silk-worm which it attacks ; but it seldom shows itself externally 

 until afterwards, when it rapidly shoots forth from beneath the 

 skin, especially at the junction of the rings of the body. Although 

 it spontaneously attacks only the larva, yet it may be communi- 



