Monthly MUTiiscoplciil 1 / 90^ ^ 



Journal. Aoril 1. 1870. >. •^^"-' / 



PKOGEESS OF MICEOSCOPICAL SCIENCE. 



The Peculiar Out-growths of Bridgesia Spicaia. — At tlie meetiug 

 of the Scientific Committee of the Royal Horticultural Society, on 

 the 2nd of March, Dr. Maxwell T. Masters reported on the above 

 structures as follows : — " The peculiar out-growths of this plant are 

 protruded from the young shoots above the axils of the leaves, and 

 above the branch proceeding therefrom. In the fully develojjed state 

 they are about the size of a large pea, of a yellowish colour, and have 

 a general resemblance to the tufts of hair found in similar situations 

 in Pereskia. In the youngest condition the excrescences occur in the 

 form of small, smooth, conical projections, covered with an outer 

 layer of small oblong cells, the outer walls of which are thickened ; 

 subjacent to these are four or five rows of small, sj)heroidal, densely- 

 packed cells, also cortical in their nature. These overlie a mass of 

 ordinary cellular tissue, the cells of which contain chlorophyll. 

 Running into this conical cellular projection are two rows of small 

 s^jiral vessels, which converge towards the apex of the cone, and form 

 a loop. These spiral vessels are continuous with those of the vascular 

 circle of the branch, and are sui'rounded on all sides by oblong thin- 

 walled cells, whose long diameter is parallel to that of the spiral 

 vessels, and more or less at right angles to the direction of the 

 parenchymatous tissue of the cortex and also of the medulla. Tlie 

 constituent cells of the medulla are si)heroidal, and destitute of 

 chlorophyll. Here and there spiral vessels traverse the medulla, 

 quite isolated from the general vascular circle. In the more fully- 

 developed excrescences the appearances are similar, excejDt that the 

 outer epidermal cells now show themselves in the form of long 

 cylindrical cells (hairs), some of which are club-sha2)ed at the 

 extremity. Some of these hairs appear to be uni-cellular, while 

 others show one or two transverse i3artitions. The hairs in question 

 are rather thick-walled, and contain a few scattered small highly 

 refracting granules (starch ?) resembling the granules found in autumn 

 when the leaves have assumed their autumnal tints in consequence of 

 the decay of the chlorophyll. From these appearances the inference 

 seemed to be that the growths in question were of the nature of 

 adventitious roots covered by hypertrophied epidermal hairs. " 



Icicles in Plant Cells. — In the ' Comptes Rendus ' for February 

 2l6t there is a paper by M. Prillieux on this subject. He has esta- 

 blished the existence normally of large icicles in the interior of all 

 frozen plants. These icicles form small columns, perpendicular to 

 the surface, and often penetrating the epidermis. The ice is formed 

 from liquids derived from the cells. The cells themselves remain 

 intact, so that there is no destruction, but simply a separation of 

 organs, and therefore what has been said concerning the death of 

 plants by freezing goes for nothing. 



